This is a very popular drink all around central Asia and is also known as kumis or airag. Fermented mare’s milk is an absolute snorter and truly disgusting!
The milk is left for a few days whilst bacteria acidify it and yeast make it slightly carbonated and slightly alcoholic.
It tastes like slightly fizzy, gone off milk. Very grim indeed.
An interesting fact though is that Kumis has been touted as beneficial for a range of chronic diseases, including tuberculosis, bronchitis, catarrh, and anemia. Kumis-based health spas even started cropping up in the 1800s. Short Story writer Anton Chekhov, a long-time TB sufferer , checked into a kumis cure resort in 1901. He drank four bottles a day for two weeks, gaining twelve pounds but no cure. So much for that!