Keg/bottle and drink as soon as possible. Fruit flies are literally dripping with acetobacter, which turns alcohol into vinegar: it's a defense mechanism. There's no sense in adding to the beer. The clock is, in my very humble opiniong, against you, especially if your fermenter wasn't air tight: acetobacter only works in oxygenated environements.
Be also aware that if acetobacter has taken hold in the beer, anything plastic that touches the beer might become irremediably tainted since the bacteria will happily thrive for long periods of time in scratches or cracks in equipment, even after a careful cleaning and sanitizing regimen has been employed.
If you have a problem with fruit flies, you might want to set up a few traps around the house and make absolutely sure that there's no spilled wort or anything else left to fester/ferment in your brew room or around your equipment. Fruit flies are attracted by anything that ferments.