Fruit Flies are commonly identified as Drain Flies because they are attracted to the bacteria found in sink drains.  For the reasons detailed in this article, you should eliminate Drain Flies-Fruit Flies as soon as possible.
If you see drain flies hovering around your sink drains, The fastest way to get rid of drain flies is to boil 2 cups of White Vinegar, then sprinkle baking soda into all your sink drains. Follow that step by pouring a small amount of boiled vinegar into each drain to kill drain flies in your house.