Frozen beer usually remains drinkable after a single freeze, but multiple freezes and thaws breaks down the beer and separates its contents, which reduces the quality. Unlike many types of perishable foods, no danger comes from freezing and thawing beer. However, subjecting beer to extremely cold temperatures causes flakes to form, which make beer less palatable to drink.
Generally, beer frozen just once for a brief period of time retains its quality. As a general rule of thumb, beer that is clear after thawing tastes the same as when initially packaged and purchased. However, turning over beer cans to remix the contents is key.