I've heard of several options. I saw advertised a special UV lamp that claims to ward them away. Some people use bleach, (...in my mouth?) rubbing alcohol or dish washing soap. After a few clicks around the internet I found this natural 'make it yourself' idea over at The Natural Singer blog.
Now, when we travel in the RV, "make it yourself" cleaners are often not practical unless you plan and make them ahead because unusual ingredients are often required and you can only carry around a small number of 'unusual ingredients' in an RV. But every RVer has these simple ingredients in the cabinet. And it's cheap and easy to make.
Need: Baking soda, water, white vinegar
Pour about 1/2 cup of water into a glass. Add 2 tablespoons of white vinegar and 2 tsp of baking soda and mix well. Place your toothbrush (es) into the glass and leave for about 30 minutes.
Rinse well (unless you want pickled teeth.) Now you have a happy toothbrush!
Vinegar and baking soda are both effective disinfectants and, in addition to disinfecting your toothbrushes, can be used throughout your RV or home as an alternative to toxic commercial household cleaners.
Do you have any easy to make and travel with natural concoctions? Please share them below then check out all the other comments for ideas.