PVC pipe toothbrush holders. Drill a hole in the top and hang on a Command hook. Slip the cap on (don't glue, and you can take them apart to wash them later). Note this is inside the cabinet, protected. Best Toothbrush Holders by Crafting in the Rain
Here's a quick and easy DIY project to get rid of toothbrush and toothpaste clutter on the bathroom counter. I used empty Crystal Light containers and Scotch Multi-Purpose Velcro fasteners. Easy to clean, too!