My cook-up this month is actually a bubble-up! Kvass is a fermented, probiotic, fizzy drink made with rye sourdough, a bit of sugar and some water. . With these three, simple ingredients you can bring to life an historic drink which has become known as ‘Russian cola’ – it really does taste like it! . Follow the link in my profile to find me walking you through the process – clear instructions, lots of pics and a few videos too.