I have had just a swarm of them in my house! My daughter says that spraying just plain old alcohol around (just as you would insecticide) will kill them. I'm trying that and it does seem to have helped. I've also been keeping the drains in the sinks, bathtub covered as much as possible and that, too has helped. I don't have too many of the flies left in the kitchen or rest of the house. There is also a product to treat drain flies that you can get at a professional exterminators store that also helps.
Frankly, I've taken a perverse pleasure in putting a banana peel or such in the oven and when they are all over it, turning on the oven and cooking them!