First check your drains to make sure that the traps haven't dried out. Then make a fruit fly trap by using a small glass jar with a little wine or apple cider vinegar in it. Put a sheet of Plastic wrap over the top. Hold firmly and cut a slice across the middle, leaving a small amount uncut on each side of the slice. Set on counter and wait. They will go in to get the contents but cannot get out.
Here are some suggestions for you.
We had terrible gnats this year as well! We did two things and it's helped tremendously! First we sprayed our house where they seemed to be gathering... the soffits and facias, the foundation and on the walls of the exterior where they were the most with THIS PRODUCT. (It says it will last 12 months and will keep lots of other insect critters away as well) The first few days we saw tons of dead gnats on the porches and patios, but now they're just gone. BTW, I did call the company to be sure it wouldn't harm birds etc. if they ate the dead bugs, and they said it wouldn't.
Then we also sprinkled THIS ALL NATURAL PRODUCT through all the foundation plantings and most of the yard, concentrating closer to the house. It will repel mosquitos, ticks, fleas, chiggers etc. Amazing difference!! I was getting eaten alive just watering, now there are very few if any mosquitos biting me. Love it!!