You can make an inexpensive anti-fog glass spray to keep your bathroom mirrors and the inside of your car's windshield fog-free. This solution keeps condensation from collecting on these surfaces.
Pour 2 ounces of white vinegar in a medium sized bowl.
Add 1 quart hot water.
Dip a clean, lint-free cloth into mixture.
Lightly wring out cloth.
Wipe mirrors and the inside of car windshields with cloth.
Allow to dry.
Make sure mirrors and inside of windshield are clean before you put the solution on them.