I was wondering if there is a quickly evaporating solution that effectivly removes fat from glasses, but does not ruin plastic or metal. That is any eyeglass frame material..
Diethyl ether, found in gasoline engine starter sprays, is a very effective solvent for fats, and it does not attack most plastics too rapidly. Try a bit on an out-of-sight location to be sure it does not damage the frame or lenses.
Note that some engine starter fluids contain an oily lubricant, which would defeat your purpose. Also note that ether is extremely flammable. A gently pressed spray can releases only small amounts at a time, but it will still catch fire if there is ny source of ignition nearby.