Oushka is a strong alcoholic spirit, favored by soldiers and members of the lower classes. Like most strong spirits, it is something of an acquired taste; upon returning from his two months behind enemy lines, Valder discovers that he's lost his taste for the stuff. The worst alcoholics tend to prefer this drink as it carries a significant alcohol content and be relatively cheap.
Oushka can be produced from a variety of materials. Asha of Amramion's father Abden Ildrin's Son made his out of corn whereas Ezdral the Sot enjoyed Adréan's Pure Barley liquor from Sardiron of the Waters which is clearly made from fermented barley.