You can easily get rid of gnats by making a homemade gnat trap using apple cider vinegar and dish soap.
Mix some apple cider vinegar with some dish soap in a jar and cover the top of the jar with some plastic wrap and secure it with a rubber band.
Poke holes in the plastic wrap just large enough that the gnats can fly into the jar but won't easily fly out of the jar.
You can also use pieces of bananas or other fruit in the jar to attract the gnats along with a little bit of water.
Pouring some bleach down sink drains also helps to get rid of gnats and be sure to put any fruits and other food away that the gnats are attracted too.
Using fly trap tapes that you hang up in your house can also trap gnats as it works for me in my kitchen.
It catches flies as well as gnats.