Kvass is a slavic and baltic traditional beverage made of bread, wheat, rye or barley. It’s very common in Russia. The alcohol content is very low with max. 1%Vol. and the kind of bread used as well as other ingredients like malt, herbs or fruits give the kvass it’s special flavour. Like other lacto-fermented beverages kvass is a good source of Vitamin-B. In Russia Kvass is classified as non-alcoholic.
It’s very easy to make kvass – you only need hard, old bread which may be roasted and then submerged in water. 100-200g bread/Liter water. The next day filter the bread over a cloth and collect the water. Lactic acid bacteria which is normally present an bread and grains starts the fermentation. You may add yeast and a tablespoon of sugar to make sure that it will ferment. 2-5 days later you can drink your Kvass and it should taste like sour beer. Adding more sugar, fruit juice or fruits may increase the alcohol content significantly.
Here is a recipe from Russia and a Youtube video