What will kill fruit flies

place bowls of apple cider vinegar covered with saran wrap and poke holes in the top

First you need to be sure all your fruit is contained or in the refrigerator. They breed in the fruit and come home in it from the store. Second they will live in the sink drains if the fruit is out of their reach. I spray Simple Green in ALL drains when I see any fruit flies in the house (showers, tubs, bathroom sinks, utility room sinks, kitchen, etc, ALL drains). You can buy it at Walmart. For fruit flies I use the concentrate to spray each drain 2 or 3 times every day until I no longer see any. Then I use the Simple Green in my regular spray bottle (1 part concentrate to 8 parts water) in my drains once a week to keep them gone, or at least in the kitchen sink. Simple Green is non toxic to humans and kids but kills all kinds of bugs and germs. It also deodorizes. I use it for all my house hold cleaning. You can get it at Walmart or Menards in spray or concentrate.

We use small bowls or cups with 2-3 drops dish soap mixed (don't make bubbles!) with 1/2 cup white wine and a little water. The flies are attracted and fall in and drown, since the soap breaks the surface tension of the liquid.

Spray rubbing alcohol on them And of course eliminate the source.

Fly strips work real well when you have a lot of them, to bring them under control quicker. I put boiling water down the drain to get rid of the ones that hang out in the trap for the moisture. Make sure any produce you leave on the counter are washed immediately when they are brought in the house. Do not leave anything thin skinned out as they will lay their eggs under the skin. If they are in your house plants, they will need to be repotted with fresh soil and the pot cleaned out well, they lay their eggs in the soil. Of course put out an attractant, be they one of the ones used in the above comments or purchased.

In addition to previous responses, make sure they are fruit flies and not plant gnats. You'll need to treat them differently.

a product called BEAP (bug eliminator and protector) - we got in online.

Here's a tutorial I wrote that might help you - https://chascrazycreations.com/diy-bug-repellents-traps/