It’s important to clean the inside of your reusable water bottles to remove grim, mildew and bacteria. But getting a brush through a narrow opening can make it very difficult to scrub clean. Instead, fill the bottle halfway with a mixture of white vinegar and water, then add several ice cubes and screw on the cap. Shake vigorously. The vinegar will disinfect, and the ice will agitate, loosening all the grime inside. Dump it out, rinse with water and you'll have a perfectly clean water bottle.