We have Gnats

We have been dealing with gnats for a couple of weeks. I have no idea why, we have no old fruit. My mother in law has the best solution. Mix half a cup of apple cider vinegar with a tablespoon of dishsoap and leave setting out. By the next day there will be no gnats. I do not know why they love this liquid mixture but they do. Do you see all the little black things, those are gnats. It did not seem like there were that many. This was in my bathroom. Who get's gnats in there bathroom and if so how? Now they are in my kitchen AGAIN. So I have the same mixture in my kitchen window.
I just hope once they are gone, they stay gone because it is driving me batty.
Pamela