Ultimately, the most effective way of getting rid of flies is by using a professional fly control service. But as this may not always be a feasible option, there are some cost-effective methods you can try at home.
Pour a sweet liquid, such as sugar water into the bottom third of the bottle.
Next, turn the top third of the bottle upside-down to act as a cone and place it in the opening of the larger part of the bottle.
As a result, flies will make their way into the bottle but will be unable to get out.
Vinegar and dish soap fly trap
First, take a shallow bowl or dish and fill it with an inch of apple cider vinegar and a tablespoon of sugar.