Have you ever heard the adage "sloppy drinkers get E. Coli?" Probably not, but it's true. Schmidt says that water should only go one way: into your mouth. Sloshing it back out into your water bottle (colloquial term: backwashing) can lead to a greater risk of infection.

Since bacteria thrive in warm, damp places, it's important to keep your water bottle clean. But skip the dishwasher: If you really want your bottle to be as germ-free as possible, you need to hand wash it. Schmidt says that the cylindrical shape of water bottles makes it hard for a dishwasher to thoroughly clean the inside. You want to wash your water bottle the way you would wash a baby bottle: with soap, water and a bottle brush. Schmidt washes his water bottle once a day.