How can you revive a drowned fly?

You can't revive a drowned fly. Flies, like all insects, breathe through tiny tubes called tracheae, which are filled with air. When a fly is submerged in water, its tracheae fill with water instead of air, preventing it from breathing. This leads to suffocation and death.

There is no way to remove the water from the tracheae and bring the fly back to life.