Like a fruit fly.but not.

These flies are identical to a fruit fly in size and shape, but are not. They are all black, including their eyes. We are fairly clean people, not allowing any old food to remain in the house, and keeping a sanitary house and bathroom that anyone should be willing to use. In the last week, there has been a massive hatch of these small flies. They perch all over the place, on the roof, cabinet doors, furniture, everywhere. Like a fruitfly, they are slow and clumsy on foot, but are quick and agile in flight. We have vinegar jar traps out and flytape. This catches some, but more seem to come from nowhere! They love my beer when I open it when I come home from work, and they even invade my wife's tea. I keep the cans out of the house for this exact reason, but it doesn't seem to make a difference. We buy a lot of roadside produce {it tastes much better than the store suppliers} so it is possible that they came from there. They are not drainflies, because their wings are the same as a fruitflie's. We have killed a couple of hundred with the flyswatter on big expeditions, but the survivors have started hiding in dark corners, like a housefly. And, like a housefly, when you train them, and you get near, they'll take off! I'm sure this massive hatch will pass on, but could anyone out there tell me what type of flies these are?