A tested method of clearing out those pesky fruit flies without using tons of chemicals is to make a fruit fly trap.
Simply take 2 tablespoons of apple cider vinegar, 1 tablespoon of sugar, a few drops of dish soap, 1 litre of water and put it in a container.
Mix it well and place the container in the location you notice the most gnats. They are attracted by the vinegar but die after touching the soap. You can set up multiple of these traps around the bar for a non-toxic sure-fired solution.
