Tips on preventing bathroom mirror from fogging up?

Does anyone have tips on preventing the bathroom mirror from fogging up after a hot shower, or while using hot water in the sink beneath it? I have tried the method of rubbing the mirror with a bar of soap, that didn’t work. I have used products meant for the car, a fog preventative spray, that didn’t work (nor did it work on the car windows either). Does anyone have a method that works, other than taking cold showers or opening a window when using hot water?