Kvass

Kvass is a fermented cereal-based low-alcoholic beverage of cloudy appearance and sweet-sour taste. Kvass originates from northeastern Europe, where grain production was considered insufficient for beer to become a daily drink. The first written mention of kvass is found in Primary Chronicle, describing the celebration of Vladimir the Great's baptism in 988. In the traditional method, kvass is made from a mash obtained from rye bread or rye flour and malt soaked in hot water, fermented for about 12 hours with the help of sugar and bread yeast or baker's yeast at room temperature. In industrial methods, kvass is produced from wort concentrate combined with various grain mixtures. It is a popular drink in Poland, Russia, Ukraine, Belarus, Lithuania, Latvia, Estonia, Moldova, as well as some parts of Finland, Sweden, and China.

Source: Wikipedia