Fruit Fly Trap Diy Without Vinegar. You can fill a plastic bottle or other containers halfway with red wine, and place a paper cone down the bottle of the neck and leave it in an area where fruit flies are gathering for a homemade gnat trap. For white vinegar, you can make a trap in which the fruit flies will come diving right into it.
Fruit flies seem to be more active at night, so you will want to set your trap out at night. This works great as an outdoor bait. Each hole should be large enough to allow a fly to enter the jar through the holes.
If you don't have any vinegar on hand, you can also trap fruit flies by placing a piece of overripe fruit in an open plastic bag.
All it takes is cider vinegar, a jar, dish soap, and plastic wrap. (it doesn't have to be full — nearly empty will also work.) (apple cider vinegar is useful for so many other things!) make a large cone out of paper and stick it in the cup (i prefer to use a disposable cup for this). I used four classic diy methods to trap (and kill!) fruit flies.