You take your trusty water bottle almost everywhere. If you worry that it has a less-than-fresh odor, even after washing, fill your bottle with 1 part hydrogen peroxide and 2 parts water. Let this sit for a few hours then rinse with warm water and let air dry. The peroxide will have killed the odor-causing bacteria that lurked in your plastic, stainless steel, or glass bottle. Your water will taste fresh again.