Fill one spray bottle with 3 percent hydrogen peroxide, which is available at any drug store. Fill a second bottle with plain white vinegar, though apple cider vinegar is also effective.
Spray the equipment with one spray bottle, then immediately spray with the other. It does not matter which one is used first, but they must be sprayed in rapid-fire succession to be most effective.
Rinse well with water, though if a small amount is left on a mouthguard, there will be no lingering taste. Neither substance is toxic in small doses.
Let dry thoroughly. The sprays will kill all salmonella, shigella, and E. coli bacteria, and will be more effective than chlorine bleach.
Store the remaining liquids in separate containers. Do not mix hydrogen peroxide and vinegar, because mixture creates a chemical, peracetic acid, that can be harmful in strong concentrations.