Beer is a food item which, when drank, heals 100 life points and temporarily increases the player's Strength by 4%, however it also decreases the player's Attack temporarily by 7%. It cannot be brewed by players.
Drinking multiple mugs of beer in short succession cannot bring a player's Strength bonus beyond 4% of the baseline value. Such an act, however, can repeatedly cause a penalty to a player's Attack until it reaches a minimum of 0. However, even if the player drinks multiple beers, they are still able to wield weapons of their base level (e.g. If a player with 60 Attack drinks beer to lower their level below 60, they can still wield dragon weapons).
During the Vampyre Slayer quest, a player will have to give Dr. Harlow a beer before he gives them a stake in which you use to finish off the vampire.
By using a beer glass on a beer barrel in a player-owned house (however this beer will disappear upon leaving the house)
By using a beer glass on any barrel with a small spout that has the examine info "It's got ale in it", "The barrel is full of ale" or "Mmm...beer!". This does not work on the barrels in Gunnarsgrunn or from the taps in most pubs