Brush the night guard.
With a designated soft toothbrush and mild antibacterial soap, lightly brush the mouth guard to clean it. Don’t use toothpaste for this, since it is abrasive and could damage the mouthguard.
Deep clean the mouth guard weekly.
Get into the habit of cleaning the mouth guard every week. Use an over the counter denture cleaner, and soak the mouth guard in it with some water. Wait until the cleaner has completely dissolved in the water.
You can do the same thing with hydrogen peroxide and vinegar. Soak the mouth guard in distilled vinegar for 30 minutes, rinse, and the soak it in the hydrogen peroxide for an additional 30 minutes, and then rinse it again thoroughly.
You can also try a combination of mouthwash and water. Use a capful of mouthwash diluted in water (until the mouth guard is fully submerged). Let it soak for 30 minutes.
Place the mouth guard on a clean surface and let it air dry.
After you have cleaned the mouth guard, let it air dry completely before putting it back in its case. This will prevent bacteria from growing in the enclosed conditions of the case. It should take the mouth guard no more than 15-20 minutes to dry.