The medieval Mongols had a few unusual drinking habits that gave their foreign associates (notably Marco Polo) a bit of a pause. Firstly, the Mongols had a ritualistic approach to drunkenness during their great feasts. Everyone was expected to partake, and everyone was expected to get absolutely slovenly. Vomiting, however, was prohibited.
When the Mongols were out on campaign, they might end up in circumstances where water was in short supply. However, the one thing that was never in short supply was horses. Thus the Mongols would prick their horses to drain their blood (without killing them), and drink the blood to restore their strength. Just another example of why the Mongol army was amongst the most self-sufficient in the Medieval world.
A particular delicacy for the wealthiest Mongols was Kumiss — fermented milk that came from a horse or camel. Horses and camels are not particularly known for producing large quantities of milk, and so it took a great number of these to produce reasonable quantities of Kumiss. For the wealthy, it was something to drink all summer long. For the poor, it was more of a twice-a-year affair.
– A few thoughts from your friend Saxo