So, if you're feeling adventurous (and desperate), you can try using vinegar to keep flies at bay. Just mix equal parts water and vinegar in a spray bottle, and spritz it around the area where you'll be hanging out. It might just do the trick, or it might just make your guests wonder why your yard smells like a salad bar.
What Does Apple Cider Vinegar Do To Fruit Flies at Jean Begaye blog
But wait, there's more! You can also try using other types of vinegar, like apple cider vinegar or balsamic vinegar, which might have a stronger scent than plain old white vinegar. Just be careful not to overdo it, or you might end up with a yard that smells like a vinegar factory.
