Drosophila fruit flies are a common (and very good) food for a wide range of amphibians, but in some cases, the adult flies are not quite right. Some slow moving amphibians can't (or won't) chase and catch flies, and some enclosures let fruit flies escape (which is never good for domestic harmony!).
Don't overlook the larval (maggot) stage of Drosophila as a convenient food for amphibians. I have not found any small amphibian which is not keen on these - their movement stimulates a good feeding response and they obviously taste good too (no, I haven't tried them)!
Drosophila larvae are particularly useful for newly metamorphosed newts and salamanders, but as they are very nutritious and energy-rich, they are a good food for any rapidly growing amphibian, or any animal you would like to fatten up a bit - try them out. And as an added bonus, you won't find the larvae winding up in your beer, or stuck on your soap!