to abandon a can of beer without completely consuming the alcohol inside it. usually, this beer will be a keystone light. Also, a drewed out beer will usually be found in the near vicinity of other drewed out beers... in part because the culprit usually commits the act muitlple times, but also because these poor, insecure, abandoned beers tend to get lonely. A synonym of drewed out is "wounded soldier".
dude, there were so many drewed out beers left in my room last night.