How to stop reef sandals from smelling?

Could you elaborate on some of the potential causes of reef sandals developing an unpleasant odor, and provide some practical tips or methods for effectively eliminating or preventing such smells? It's quite common for footwear, especially those worn in wet or humid environments, to accumulate bacteria and other microorganisms that can lead to unpleasant odors. Understanding the root of the issue and implementing effective cleaning and maintenance strategies could significantly improve the overall freshness and longevity of one's reef sandals.