Build the King of Fly Traps (I usually like to pin stuff that takes you directly to the article, but this is a great pic of the end result. And so there is one more click to get to the real instructions...sorry 'bout that.)
Want to get rid of pesky fruit flies? Put about 3/4 cup Apple Cider Vinegar into a small bowl. Add a few drops of dish soap. Find a spot near where the flies are swarming to set the bowl and leave overnight.