What is working: Put a couple of tablespoons of apple cider vinegar, a table spoon of water and a couple of drops of dish washing soap in a cup. (I use the bottom halves of plastic bottles so I can throw them away when they catch a disgusting number of fruit flies.) Swirl the cup to get a layer of suds. Place the cups where the fruit flies hang out. The fruit flies try to get the vinegar but the soap has broken the surface tension and the fruit flies drown.
P.S. For PETA members or anyone who wouldn’t harm a fly, there are instructions on the internet for "catch and release" fruit fly traps.