It's mildly alcoholic and slightly fizzy — fermented mare's milk that Kazakh herders have brewed the same way for over 2,500 years.
Kumis is made by fermenting raw mare's milk with lactic bacteria and yeast, producing a tangy, effervescent drink with a light alcohol content. It's traditionally made and sold at roadside stalls and yurts during the summer grazing season, when mares' milk is most plentiful.