Flies are among the most common pests and can multiply quickly. While purchasing fly traps from hardware stores and grocery stores is always an option, you can easily make your own homemade fly traps from a few simple ingredients that are probably already in your kitchen pantry.
Rinse out an empty 1-gallon milk or water jug, and cut a few small holes all over the jug, about the size of pen caps. Do not cut any holes in the bottom 4 inches of the jug, as this is where you will add solution. Pour 1 cup of syrup, molasses or fruit juice into the container, along with 1 cup of apple cider vinegar. Twist the cap back onto the jug, and place it in the yard or location where flies are heavy. Empty the jug every few days and refill, or toss the whole jug and start fresh with a new container.
Sugar and soap is another combination sure to catch fruit flies as well as larger flies. Take a small bowl or jar, and pour equal parts of sugar and liquid dish soap together. The sweet smell of the sugar will attract the flies, while the soap will grease their wings, taking away their ability to fly and thereby drowning them in the solution. This is good for indoors, as it does not let off a sour smell like vinegar solutions.
You can also create a fruit bait trap that will attract flies, as well as outdoor pests like wasps and honeybees. Cut the top third off of a 2-liter bottle, and flip the top part upside down into the larger bottom half. The mouth of the bottle should now be pointing downward, creating a funnel effect. Tape the two halves together, and pour in 1/4 cup of vinegar and 1/4 cup of liquid dish soap. Add a splash of fruit juice or a piece of freshly cut fruit into the jar. Insects will be attracted to this and enter the funnel but be unable to find their way back out.