Beer comes in big 750ml bottles in Nepal and they cost only 200NRP (less than 2 Euros). There are several options too. Nepal Ice, Everest and Gorkha are the ones I liked. Nepal Ice being the lightest one. But these are the options for average tourists. For the more adventurous ones I recommend trying things brewed at home.
The culture of Nepal is quite accepting of drinking and almost every house in a village brew their own booze. The home made beer is called 'Chhang'. Depending on the village of origin, it tastes and smells between strange to horribly repulsive. In some parts you may also find home made spirit, called 'raxi' (also spelled 'ragsi' on hotel menu). Same applies to 'raxi' regarding smell and taste.
Nepali men usually lose control when they drink, so be careful. Most start talking really loud. Some would start singing or dancing - I liked the ones of that kind. Have mixed feelings about another kind I found who start speaking English after a few a shots and believe alcohol improves ones English language skills.