For gnats, I take a small ramekin and add a little dish washing soap, some apple cider vinegar, and some orange V8 Splash (once I started finding them in my glass, I realized how much they love it!). Leave one out wherever you see the gnats gathering, and within a day or two, you'll have dead gnats floating in the mix. I find that it tends to evaporate rather quickly, so if you continue to have issues, top it off before you see it dried out.