Set It Up
Pour some apple cider vinegar into the bowl or jar. Add a few drops of the dish soap. The vinegar acts to attract the flies ,while the soap doesn't allow them to land on the surface of the liquid. This causes the flies to fall in and drown.
Pick a Spot
You will need to place the bowl in an area where you have seen the fruit flies. The more accurate this location, the more effective this technique will be.
Allow the bowl to sit for the entire day and maybe overnight. Check on the bowl periodically to ensure that it is working.
Once all the flies have had their vinegar goodbye, flush the liquid (and flies) down the sink and rinse and wash the bowl or jar.