There are a few different ways you can get mold out of your CamelBak mouthpiece. One is to use a Q-tip dipped in alcohol to remove specific residue before soaking it in bleach. This will kill any mold that was present in your mouthpiece. A method that is less harsh than bleach is to soak the mouthpiece in white vinegar, as white vinegar is known to naturally kill mold. Always make sure any residue is gone before using the mouthpiece again. If you're concerned, you may be able to replace the mouthpiece entirely.