I've got dryer sheets shoved in crevices of 3 vehicles and don't see any mice or evidence of them, but I don't go looking either. I've also used bars of soap in a ziploc bag with holes in it. As stated by others any smell will fade and need to be reapplied but these don't have the lingering stench of moth balls. Or anyone's balls.
I tried that one my motorcycle one year. Mice like to build a nest where the battery goes. So I shoved a few dryer sheets in there. Little bastards made a nest right on top of the drier sheets.