You should keep your sink clean and dry after using it to avoid those insects inffestation. I'm not sure it's fleas - they just can't fly. Fruit flies and other little house flies can be killed with Zyrox granules. It's very effective, but you have to remember that it's toxic, so if you have pets they shouldn't touch this stuf. Here is the article where one can find the description of other good remedies against flies.

I feel nauseous after semi-successfully fighting off these flying objects around the sink. Usually they're fruit flies, around the summer, but these, aftering finding an old pototo, are much smaller. Anybody have suggestions what the public health department will tell me tomoroow, when I ask for advice? I'm too tired to even correct my typos, and am losing my apetite too...I'd been using a couple of drops of soap in apple cider vinegar to date, which seems to be working, but I'm impatient, and want to eat comfortable again without this type of uninvited company.