Porky Pig tried this once in an old Bug Bunny cartoon.
He had a mouse problem, so he bought a cat.
When Porky Pig went to bed, the cat invited all of his friends over and they got wasted played the piano loudly and sang drinking songs. One of the cats had a lampshade on his head and everything.
When Porky Pig got fed up with this, he bought a dog. How he found a place in the 50's or 60's that sold dogs in the middle of the night is anyone's guess. He let the dog loose in the house and waited.
The cats got the dog drunk and he was singing with them in about 30 seconds.
So obviously these flies are eventually going to get drunk and sing, which is pretty cool, making this plan sweet.