This question already has an answer here:
Today I had lunch in a small Mexican taco place, and they had hanging, in the middle of the room, two clear plastic bags filled with water:
I asked the reason for the hanging bags of water, and was told it's intended to scare flies away. Allegedly, the combined effects of make-shift prism, along with a fly's compound eye, alters the flies' perception of... something (??) such that they are confused, or frightened, or otherwise repelled from the area.
It strikes me as a completely ridiculous claim, but it's clearly taken as serious enough that someone actually went to the effort of hanging mistletoe-like water bags, and the friend I was with was also familiar with the old wive's tale.
So, is there any reason to think that bags in this configuration would repel flies?