Our regular group of 5-7 has Friday Night libations. Not everyone partakes but everyone knows and has fun with it. It's our Guild Raid night too. But we only fill with people who know whats up and enjoy the stupidity. We also tend to keep it easy going. (VoN 5-6, DQ, L Hound, Fire on Thunder Peak, Morgrave, & Dryad to finish off since by then the dance is real fun!)
I know people drink all kinds of stuff - Whiskey, Rum & Coke, Captain, Beer - I myself tend to burn through a Tumbler of Sangria (or two) during the fun. As I am the tank I do find it funnier as the night goes on watching others bounce off walls or "Search for Secret Doors" as we call it. Being tanky means I can miss a step and still survive. Others don't have that benefit.