Russian Bread Kvass

Russian Bread Kvass is a favourite in our house.

It’s sweet, it’s sour, it’s bubbly, it’s rich. And that’s before you’ve flavoured it – which you can do with fruit, herbs, spice and roots.

Kvass is a less-well-known cousin to water kefir or kombucha. It’s easy to make and full of probiotic goodness. All you need to start it off is some sourdough rye bread. And you can keep that bread – using it over and over; it’ll just get stronger and tastier.

My hubby, when I first started making it, commented that it tasted like Cola – indeed it is known as ‘Russian Cola’, comes from the Slavic and Baltic regions, and has been around for over 1000 years.

Some recipes you can find online use bread yeast to start the fermentation. I don’t and I’ll show you that you don’t need it – wild yeasts captured in the sourdough and omnipresent in our environment do a fine job of weaving their magic on this drink without the need for industrial yeast.

A by-product of yeast fermentation is alcohol, and kvass is slightly alcoholic – usually 0.5-1.0%. In the summer it’s refreshing straight from the fridge and in the winter, it’s a warming, fizzy treat!

Russian Bread Kvass



1 cup of cubed sourdough rye bread (can be stale)

1/2 cup sugar

3 to 4 cups of non-chlorinated water


Herbs/spices/fruit/flavourings/extra sugar or honey (for flavouring the second stage of fermentation).


These specific pieces are not strictly necessary, but will help you a lot.

1 litre/1 quart glass jar with lid

small plastic sieve

small funnel

1 litre/1 quart swing-top glass bottle (for the second stage of fermentation)

Swing-top bottle and glass jar, both full of kvass.

Let’s look more closely at what you need:

Sourdough rye bread

The sourdough rye bread is used as the starter for this fermented drink.

If you don’t currently make this, it’s a great opportunity to give it a go. I have a course that’ll guide you step-by-step through making rye sourdough whether you’re a newbie to sourdough or an experienced baker. It’s called Rye Sourdough Bread: Mastering The Basics, and you can check it out here.

If you aren’t up for making a rye sourdough, go find a baker who is. Supporting local artisanal bread is such a good thing! Do take care that you are purchasing a true sourdough – not one labelled as such but instead made with commercial yeast and sour flavourings, not a wild yeast starter.

You only need 1 cup of bread cubes – not much – and it can be stale. The end of a well-loved loaf is perfect!


I use a mix of two-thirds whole dark brown sugar and one-third golden sugar. This gives the resulting kvass a dark colour and a rich, deep flavour that compliments the sourdough rye extremely well.

You don’t need to do this though; use whatever sugar you have to hand or fancy trying.

Sugars I often use in kvass.

When I started making fermented drinks, I was concerned about the sugar content. I’m not anymore. How come? Firstly, I make them sour (much more so than the ‘average’ guest to my house cares for!!) which means more of the sugar has been transformed into by-products. Secondly, I know sugar is essential to the process of fermentation and that the benefits of drinking fermented beverages far outweigh the minimal sugar imbibed in the process. And thirdly, I don’t drink these beverages in quantity…even my son (who drinks the most in our house) only has 2 small cups a day.

I haven’t tried using honey or other liquid sweeteners. If you want to give these a go, I suggest you wait for your second or third round of the drink to give your starter some time to get strong and you some time to get used to how it should work.


Your water should be non-chlorinated. Filter it, or failing that, pour and leave tap water out overnight. A lot of kvass recipes suggest boiling the water first to remove potentially harmful particles. I boiled my water the first time I did this, but have not done so subsequently and have not had problems, but please make your own mind up on this – if you feel more comfortable boiling, ensure the water has cooled to below 41C/105F before you add the sugar and bread.


This is where you get to be creative!

For the second fermentation you can add more sugar – in the form of honey, dried fruit or fruit and/or other flavourings.

Fresh mint is traditional and I love it, but I’ve also added fresh rosemary.

Ginger works well, helping to make it more bubbly and give it a zing and combines well with honey or fruit.

I’ve also used coffee grinds, cacao nibs, cardamon pods, fennel seeds and my current favourite – liquorice root in stick form.

The process:

Let’s fill in the details:

Stage one – Preparing the first fermentation

If you wish to sterilise your 1 litre/1 quart glass jar you can do so by washing it out and placing it in an oven at 120C/250F for 15 minutes. Let it cool.

Toast the cubed sourdough rye bread in the oven at 120C/250F for 1-2 hours. You want it dried out and crispy but not burnt. Let it cool.

Fill your glass jar with water (previously boiled and cooled, if desired) two thirds full.

Add the sugar and stir until dissolved.

Add the cooled, toasted bread to the jar and stir gently.

Lightly screw a lid on or cover the glass jar and leave it somewhere warm and out of direct light to ferment.

Check it after 3 days (put a note in your calendar!) and taste. If it is sour enough for you, you can proceed to stage two, if it still tastes strongly sweet, leave it to ferment further (to produce a soured drink (the way we like it) mine usually takes 6-7 days).

Stage two – Decanting and (optional) second fermentation

Prepare the 1 litre/1 quart swing top bottle by cleaning and sterlising as above.

Put the funnel in the neck and balance your sieve on this (see below).

Pour your fermented kvass through the funnel/sieve, so that the kvass ends up in the bottle and the bread cubes are caught in the sieve. You may have to hold the sieve still and/or use a spoon to scrape out some of the bread to complete this.

Remove the funnel/sieve/bread and put to one side.

Add your optional second fermentation sweeteners/flavourings to the bottle. Cap the top. If necessary (it is with honey) gently agitate the bottle to mix.

Leave this bottle somewhere warm and out of direct light to ferment.


It’s ready to drink from now onwards, but will improve over the next 24 hours. Check it regularly, releasing the gas in case it has gotten very bubbly. I find it’s best drunk within 3 days. Remove it to the fridge if you want to preserve – this will virtually stop the fermentation but will also mean it looses some of its fizz.

Stage three – Making the next batch

The next batch of bread kvass is ready to make as soon as you’ve strained the bread from the liquid at the beginning of stage two.

Wash your previously used 1 litre/1 quart glass jar, or use a new one.

Return to stage one above and repeat the process from the third paragraph. I’ve found it is possible to use less sugar on subsequent fermentations, so feel free to experiment with quantites and the time they take to ferment.

If you don’t want to immediately make a new batch of kvass, you can keep the starter in the fridge for a few days until you’re ready.

Download a hand-drawn graphic that you can keep in your kitchen to help remind you of this process here.

Sharing it:

I want to see and hear about your process: your ingredients and why you chose them, how you’re fermenting them, the finished kvass, how you drink it and who you share it with. If you’re on instagram, post and tag me (@ancestral_kitchen). If you don’t have instagram, please do comment at the bottom of my blog post – you can upload your pictures there too.

Kvass during a kitchen break!

7 Responses

  • I haven’t made this kvass yet although I have made it with beets. I really enjoyed it. I had a couple questions. why does it need to be rye bread? could it be another dark bread? is the toasting essential? or could I just use the bread as is. I have some homemade sourdough squash bread from a friend that I thought might work for this but I don’t currently have a stove, just a microwave so that’s why I ask about the toasting.

    • Hi MaryLou,

      Rye bread is traditional – the kvass comes from Russia where rye is a main crop. You could try other breads though for sure. Toasting is not essential, but it does bring a lot of additional flavour to the drink due to the ‘sugaring’ reactions toasting creates. Hope this helps!


  • Made this recipe three days ago, but I’m still not seeing any reaction or yeast, reproduction or activity. I ended up putting raisins in it yesterday as I have heard raisins. Also have yeast on them. Oddly, still nothing. Curious to know how yeast can survive inside the sourdough bread, when it’s completely baked to death Before you use it?

    • I’d say be patient, stir every day and if possible up the temp in your space. I have made this many times (and so have others) and it does work. Adding raisins is a good idea to potentially speed it up. Yeasts and bacteria are present on all foods and in the air…and they do the work even when the bread isn’t ‘raw’.

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