How to Make a Fruit Fly Trap From Trash and Test the Best Bait

Fruit flies multiply quickly and can become a major problem around fruit, compost, and food scraps. I made this trap from a discarded plastic bottle, aluminum foil, a rubber band, soap, and household bait.

What this project does: This trap turns a discarded bottle into a simple way to catch fruit flies.

I also tested different bait combinations to find out which one caught the most fruit flies.

Best result: The apple cider vinegar and soap mixture caught more than 30 fruit flies overnight. I found the first trapped fruit fly after about 15 minutes, and it was dead when I removed it from the soapy liquid.

1. 1 empty plastic soda or water bottle
2. A small piece of aluminum foil
3. 1 rubber band
4. Scissors
5. A toothpick or scraper tool
6. Apple cider vinegar
7. Honey
8. Liquid dish soap
9. Warm water

Remove as much of the bottle label as possible with your fingernail or a scraper tool.

Run the bottle under warm water for at least 30 seconds, then scrape off the remaining paper.

If some adhesive remains, leave it in place. It can help hold the foil lid in position and create a tighter seal.

Tip: Dry the bottle completely before cutting it.

Carefully cut off the top third of the bottle where the tapered section becomes straight.

1. Keep the bottom section for the bait.
2. Cut slowly so the edge stays as even as possible.

Safety: Ask an adult for help if you need assistance using the scissors.

Cut a square of aluminum foil about twice as wide as the bottle opening.

Place the foil over the opening and press it tightly around the rim.

Secure the foil with a rubber band. Press the edges flat against the bottle so fruit flies cannot escape around the sides.

Use a toothpick to poke several small holes through the foil. Pull the toothpick straight back out instead of twisting it.

Why this matters: Pulling the toothpick straight out leaves small foil edges pointing downward inside the trap. Fruit flies can enter through the holes, but the edges make it harder for them to escape.

I tested three mixtures to compare which bait caught the most fruit flies.

1. Apple cider vinegar and soap: 90% vinegar and 10% soap.
2. Honey and soap: 90% honey and 10% soap.
3. Water and soap: used as a control mixture.

I used soap in each mixture because it breaks the liquid’s surface tension, making it harder for flies to land on the surface and escape.

My prediction: I expected the apple cider vinegar mixture to work best because fruit flies are attracted to sweet and acidic smells.

Add enough liquid dish soap to barely cover the bottom of the bottle.

Pour in enough apple cider vinegar to bring the liquid level about 1 inch above the bottom.

Replace the lid and leave the trap near fruit, compost, or another area where fruit flies are active.

Result after about 15 minutes: I found one fruit fly in the trap. When I removed it from the soapy liquid, it was dead.

For the longer test, I left the trap out from about 4:00 p.m. until 7:30 a.m. the next morning. It caught more than 30 fruit flies overnight.

Add enough liquid dish soap to barely cover the bottom of the bottle.

Pour in enough honey to bring the mixture about 1 inch above the bottom.

Replace the lid and leave the trap in the same type of location for the same testing period.

Result: This mixture caught only 7 or 8 fruit flies, making it less effective than the apple cider vinegar mixture in my test.

Load the trap

1. Carefully remove the foil lid without tearing it.
2. Add enough dish soap to cover the bottom of the bottle.
3. Pour about 1 inch of apple cider vinegar into the bottom of the bottle, then add only a few drops of dish soap.
4. Stir the mixture gently with a toothpick.
5. Reattach the lid and press the foil tightly around the rim.

Choose a location

Place the trap near exposed fruit, food scraps, or an open compost container.

If you cannot find exposed fruit, place the trap near the brightest window in your kitchen or near the area where food is kept.

Do not place the trap where it can easily be knocked over.

After catching fruit flies, the trap will need to be emptied and cleaned.

1. Empty the trap safely.
2. Rinse it several times.
3. Wash the bottle with soap and water.
4. Rinse it thoroughly before using it again.
5. Refill the trap by repeating Step 7.

Experiment idea: Try moving the trap to different locations to find where the fruit flies are most active.

This trap gives a discarded plastic bottle a useful second life while helping control fruit flies.

My results:

Apple cider vinegar and soap: caught more than 30 fruit flies overnight.

Honey and soap: caught only 7 or 8 fruit flies.

First observation: I found a trapped fruit fly after about 15 minutes. It was dead when I removed it from the soapy liquid.

Microscope evidence

The microscope photo shows the fruit fly I removed from the trap after about 15 minutes. It was already dead when I took it out of the soapy liquid.

If you build this trap, try placing it near fruit, compost, or food scraps and see which location works best.

Thanks to my brother for helping with the photos and lending me his microscope.

—James