Meaning:

Gwas/kwas (Russian, Ukrainian: квас, "fermented"; Polish: kwas chlebowy, "fermented on bread"; Lithuanian: gira; Estonian: kali) is a drink with low alcohol content popular in Russia, Ukraine and other Eastern European countries. "Lithuanian: gira; Estonian: kali) is a low-alcohol beverage popular in Russia, Ukraine, and other Eastern European countries, made by fermenting dried bread and resembling beer in color with a slight reddish tinge. As its alcohol content is only about 1%. In Russian cities, kvass can also refer to red tea mushrooms.

Associated story

It is said that centuries ago in Russia, some small restaurant owners collected the bread crumbs that diners dropped on the table and put them in bottles to ferment. After a few days, the bread crumbs in the bottle turned into a juice with a strong leavening aroma, and its unique flavor was loved by Russians. People also found that this drink has a digestive, gastrointestinal regulation function, and gradually become a common drink spread in Russia.