I have gone just about crazy with the fruit flies until just about two weeks ago. I used a disposable plastic cup, any funnel type object that left no gaps between the cup and itself, I used a cone like top from a childrens cup that we received at a restaurant turned upside down on top of the cup. Before I put the top on I poured balsamic vinegar in the cup, I secured the funnel with tape so the little buggers could not escape, don't be chintzy with the vinegar, you really want to attract them, It took about a week and a half but I am pretty much fruit fly free. I Just really inspect my produce at the store before I put it in the plastic baggies, I even blow on it first(I know, call me kooky) but the fruit flies drive me crazy and this has been my saviour. Good luck escaping from the little maniacs and I hope my tips work for you.
Patti
P.S.
Be patient, they mingle around the top of the trap and look really gross but they fall for it in the end, don't try swatting them away, they will only last longer.