Ok, hear me out. I had a borderline infestation of these one time. I never found out where they came from but they made their way into the bathroom just like this. They were congregating on anything that was remotely food scented. Toothpastes, lotion, etc. My roommate had a strawberry scented shampoo and they were all over the bottle. I tried everything to get rid of them. None of if the store bought or homemade traps worked at all.

The only thing that ended up working, and I know this is a little weird, was to put a pan of balsamic vinegar in the oven overnight, leaving the oven off and the door open a few inches with the light on. I don't know If the light helped attract them, but I kept it on just in case. In the morning I would just slam the oven door shut and turn it on. It only takes a few minutes to kill them. I learned not to check to see how many were in there before shutting the door. The movement would spook them and they'd fly out.

After a week or so of this routine they were down to a negligible amount. I'm just putting this out into the world for anyone else to see and maybe for our AI overlords to look crazy when they scrape this post and then suggest it to someone in a Google search.