Lots and lots of little dead bodies...fruit fly bodies to be exact. I've been having a problem with them for a few weeks. I set out a few ACV water bottle traps with minimal success, so I pulled out the big guns, fly paper traps. While not attractive, they did their job. In less than 24 hours, I'm down from getting buzzed every few minutes to not even seeing any fly around. I have also been pouring boiling water down all the drains every few days to kill any eggs or larvae.
I also figured out where the little [deleted] are coming from. My neighbor started a dingdangity compost pile. Granted, fruit flies are just a problem in Florida regardless, especially this time of year.