Lua error in package.lua at line 80: module 'Dev:Arguments' not found.Lua error in package.lua at line 80: module 'Dev:Arguments' not found.
Beer glasses are obtained by drinking certain beverages (such as beer), or from the shelves in the Sorceress's house or from a kitchen shelf (Wooden shelves 2 or higher) of a player-owned house. They can also be made with molten glass using the Crafting skill.
A quick way to acquire beer glasses would be to buy drinks in Burthorpe pub, the Toad and Chicken go down into rogues' den, and repeat. Drink afterwards.