How to Use Vinegar to Kill Gnats
Gnats, the tiny flying insects that resemble mosquitoes, are a major nuisance during the summer months. Some varieties of gnats bite humans, but even the gnats that do not are annoying due to their swarming behavior and preference for potted houseplants.
You can kill fungus gnats and other small flies in your home with a natural, non-toxic vinegar trap. The smell of vinegar will attract the insects into the trap. Since gnats can't figure out how to escape from the jar, they will drown in the vinegar.
Pour an inch of apple cider vinegar into a glass jar.
Roll a piece of paper into a funnel shape and insert it into the mouth of the jar so the narrow end is about an inch above the vinegar.
Place the trap wherever gnats are a problem.
Discard the dead gnats every one or two days. Replace the vinegar at the same time.