RuneScape Classic Wiki
RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Vodka
The Old School RuneScape Wiki also has an article on Vodka.

Vodka is used in making cocktails and can be bought for 5 coins from Heckel Funch in the Grand Tree, who is located in the southeast corner of the second floor. He also sells a variety of other supplies like Brandy and Gin, or various fruits.

When drunk it temporarily increases Strength 3-4 levels and heals 4 Hitpoints, but decreases Attack 3-4 levels.