Kvass ("leaven"), a Russian alcoholic drink, a form of beer.
It is made, by the fermentation of whatever grain is available, such as wheat, rye or barley (Common or Table Kvass), or of black bread, with the addition of sugar or fruit, usually apples. It has been a common drink in Russia since the 16th century. Though in the cities it is made commercially, usually it is home made. Kvass is of low alcoholic content (0.7 to 2.2%).