How do I stop my Reef sandals from smelling?

Hey there, I've been really enjoying my Reef sandals, but lately I've noticed that they've been developing a bit of an unpleasant odor. Do you have any tips or tricks for getting rid of that smell and keeping my sandals fresh and clean? I've tried washing them, but it doesn't seem to be working as well as I'd hoped. Any advice would be greatly appreciated!