The Russian fermented beverage made from rye bread is kvass.
Kvass is a lightly fermented drink associated with Russia and other parts of Eastern Europe. Traditional recipes soak dried rye bread, rye flour, or rye malt in hot water, then ferment the liquid with yeast, often alongside sugar. The result is usually cloudy, gently sweet-and-sour, and much lower in alcohol than beer.
Kvass has a long history in the region. Its first written mention appears in the Primary Chronicle, which connects it with celebrations surrounding Vladimir the Great’s baptism in 988. It became a practical everyday drink in societies where grain was available but beer was not always brewed for daily consumption.
A common mix-up is confusing kvass with kombucha or kefir. Kombucha is made by fermenting sweetened tea, while kefir is a cultured dairy drink. Kvass is cereal-based, and its characteristic flavor often comes from toasted rye bread. Modern commercial versions are frequently pasteurized and may include fruit, berries, herbs, or additional carbonation.