酒: sake. For most of renku's history Japense sake was the go-to alcoholic drink for inclusion in verses. Nowadays, all imaginable intoxicating beverages can find their way into linked verses: whiskey, vodka, tequila, rum, brandy, wine, beer, and so on. Be careful about beer, though; a cold beer evokes summer, so you'll want to mention it only if it's your turn to write a summer verse.
Renku is a growing, evolving art, so poets should feel free to expand the contents of its categories of experience. It's OK to mention other mind- or mood-altering drugs besides alcohol when visiting this area of the Mandala.