Clean everything. Make sure you get the egg cases, which stick to the sides of things like garbage cans and compost bins. Put anything attracting them into a sealed container or outdoors.
Then make a fruit fly trap. You can do this with a plastic bag or a canning jar. Put a little of something attractive to fruit flies (wine, vinegar, fruit peelings, whatever) into your chosen container. Leave it for a few hours. Then seal up the trap and take the flies outside. (If using a mason jar, slowly sliding the lid over the top catches much more flies than slamming it down.) If using a plastic bag, you can just throw the whole thing out. If using a canning jar, just walk a few feet away from the house, open the jar, and shake it until they all fly away.
Repeat until the fruit fly population is acceptable.
BTW, if you lost water as well, run or dump water into the drains to refill the U-bend plumbing traps under the sinks. If those traps dry out, sewer flies (which look almost exactly like fruit flies) can come up into the house.
Good luck!