We trap 'em. Take a large, wide-mothed jar and place a used banana or mellon peel inside. Leave on the counter in the morning. Then when you get home from work, sneak up on the little pests and quickly clamp the lid on top of the jar. Then, you can either throw away the jar, drown the flies inside (a tricky buisness), or release them outside. I prefer to do the little critters in. If you crack the lid and insert an eye-dropper full of rubbing alcohol into the jar, and re-tighten the lid, it will kill them.
To paraphrase Yosemte Sam, "I hates fruit flies".