Flat beer has a surprising number of uses, such as an ingredient in bread and frying batter, removing stains, and getting slugs and snails out of your garden. Like other carbonated drinks, beer becomes flat with time, so if you plan ahead, you can just leave an open can of beer in the refrigerator for a few days. But if you have a sudden craving for beer bread or beer-battered seafood, you'll need to get the carbonation out of beer a little faster.
Take the beer out of the refrigerator and let it warm to approximately room temperature.
Pour the beer in a large bowl. The size of the bowl depends on the amount of beer you're using. Use a large mixing bowl if you have a can or more. If you're using less than a can, a large cereal bowl will work.
Whisk the beer for five to 10 minutes to remove the carbonation. Let the beer sit for five minutes before using.