I wanted a fruit fly trap for my kitchen that looks pretty. So I found a pretty jar with a lid and put a trap cone in the middle. Simple and deadly!

Creality

Ender 3 Pro

No

No

.2

100%

Needs to be watertight so ensure that your infill is 100%, use thick walls (6) and adequate overlaps. Slightly hotter extrusion temp may help seal it all together also.

If your printer over-extrudes the tip of the cone, use a metal object (eg, soldering iron tip) to open it up enough for the fruit flies to make it through easily.

First check for waterproof by filling it under the sink at full force, look beneath for telltale water bubble emergence. If it's not sealed, try using polyurethane, epoxy, or whatever you would generally use to seal something up.

For the fruit flies around my house red wine is their favorite. So I fill it about 1/4 full with that and add a few drops of dish soap to ensure they have a brief and final drunk.