Hydrogen peroxide is the only germicidal agent composed only of water and oxygen. It is considered the worlds safest all natural effective sanitizer. It kills microorganisms by oxidizing them, which can be best described as a controlled burning process.
To make, heat 1/2 cup of vinegar in microwave for about 90 seconds. Add 1/2 cup of regular dish soap. (Any 1:1 ratio is fine.) Pour into squirt bottle. Spray anywhere you want to get rid of soap scum (I used this on my shower, including glass shower doors) and let sit for a few minutes. Return and wipe down with a microfiber cloth (or I love using magic erasers).