How To Build A Fly Trap With A 2-Liter Plastic Bottle

One of my favorite summer activities is grilling outdoors.

To me, the stress of everyday life melts away as I’m cooking chicken, burgers, bratwursts, pork chops and steaks while drinking some ice cold beer.  Whether it’s cooking with propane or charcoal (we have two grills), I can relax while standing next to a hot grill in the heat of the day.

Recently our small patio area has been swarming with flies.  We’ve had a hot and wet summer this year, and between the climate and my neighbors leaving crap behind their house, this year the flies have been a growing problem.  I nearly reached the breaking point when about a hundred of those damn insects began swarming me, my grill, and my cooking utensils last week.

That’s it.  It’s time to start catching those little punks and eliminating their incredibly annoying presence on my patio.

The homemade fly trap begins with an empty 2-liter plastic bottle.

An incredibly cheap and very effective fly trap can be constructed out of an empty 2-liter bottle of soda.  As you can see, I built my homemade fly trap out of a bottle of cherry Coca-Cola.  You’ll want to rinse the bottle so your fingers and equipment won’t get sticky when building the trap.

Remove the label and unscrew the cap.  After you enter your Coke rewards points onto the Coca-Cola website, punch a large hole in the bottle’s cap.  Make sure the hole is about the size of a pea.  It must be large enough for the flies to easily crawl through.  After that use some scissors and make a horizontal cut around the circumference of the plastic bottle.  The objective is to remove the top 25-30% of the bottle.

Our fly trap is now separated into two pieces and the bottle's cap has an entrance hole for the flies.

Here we have the empty 2-liter Coke bottle separated into two pieces.  You can also see the large hole in the middle of the bottle’s cap.  The hardest part of the project is behind us now.

Now it’s time to bait the trap.

Noticing how effective the barbecue sauce was for attracting the flies when I was grilling last week, I decided to use that as part of my bait.  I spread a little bit of BBQ sauce in the bottom part of the bottle.  I also heated a cup of water, mixed in a bunch of sugar, and then poured that into the bottom of the bottle as well.  The purpose of the sugar water is twofold:  sugar attracts flies, and the water will drown them in the end.

Our homemade fly trap is baited and ready to go!

Once the bottom part of the 2-liter bottle is baited, simply FLIP OVER the top part and set it on TOP of the bottom part of the plastic bottle.  This creates a funnel that’ll lead the flies right into the trap.  I used two small pieces of tape to hold the upper and lower sections together.  There’s some condensation on the interior of my fly trap from the hot sugar water.  The reddish colored smudges are from the BBQ sauce.

It's time to start trapping those little bastards!

The homemade fly trap works both inside and outside the house.  Since I’m trying to eliminate the insects from my patio, I placed the 2-liter plastic bottle fly trap near my cooking area, a place where the flies commonly gather.  Set it down and then leave the trap alone.  If you baited it correctly, then the flies will start investigating it very quickly.

The way that the trap actually works is incredibly simple.

The scent of the sweet bait (or a rotten stench if you use old meat or pieces of fruit) flows out of the hole in the bottle’s cap and attracts the flies.  The flies then land on the bottle and walk down the funnel towards the origin of the scent.  If they’re hungry enough, and they always are, then they’ll crawl through the hole in the bottle’s cap and enter the trap.  The flies will then dine on a sweet snack, try to crawl up the sides and escape (which they cannot), and then they’ll grow tired, fall into the water and then die.

Won’t the flies escape through the entrance hole?

Nope.  It’s been scientifically proven that flies are really, really stupid insects.  They commonly fly towards the light and they’ll be trapped on the sides of the container.  Some people will simply remove the bottle’s cap and leave a great big opening for the flies, knowing that most of the flies won’t figure out how to escape.  I might try that for my second version of the homemade fly trap and see if there’s a difference in the number of trapped flies.

The homemade 2-liter plastic bottle fly trap works!

I placed my 2-liter plastic bottle fly trap on my patio about an hour before I started grilling.  In that time frame my trap caught about twenty of the flies.  That evening’s grilling session was significantly more peaceful.  🙂

Later that evening I removed the top and dumped the sugar water and collection of dead flies in some bushes at the back of the yard.  In the kitchen I washed both pieced of the 2-liter plastic bottle and let them dry, allowing me to use the trap again in the future.


– Next time I’ll punch small holes into the top of the trap to allow more of the bait’s scent into the air, hopefully attracting more flies into the trap.

– As previously mentioned, some people remove the bottle’s cap entirely and leave the trap that way, giving the flies a nice and large opening into the trap.  My only concern is that depending on the size of the bottle, some flies might fly out of the large opening and escape from the trap.

– Another option is to add a small packet of yeast into the sugar water.  The reaction between the yeast and the water releases carbon dioxide, and that expulsion of gas will help push the scent of the bait into the outside air.

As a whole, I’m pleasantly surprised by the effectiveness of this incredibly simple homemade fly trap.  Grilling sessions during the remainder of the summer are going to be much more pleasant.