Gym socks or stale cheese
The hops have either gone bad or there's just too much of them. The sweaty/stinky flavor is produced by isovaleric acid, the slightly older and less vommity cousin of butyric acid.
Vinegar "If you've ever opened a beer and thought it would be better used as a salad dressing, you know the problem is infected beer," says Matt. Sour and wild beers aside, vinegar aromas are present because wild bacteria has turned sugars into acids instead of alcohol.
Dan Gentile is a staff writer on Thrillist's national food and drink team. The most common off-flavor in his beer is cheapness. Follow him to happy hour at @Dannosphere.