Bacteria and fungus grow in sweaty shoes, producing bad odour over time if the organisms aren't held in check. Keeping your Keen sandals from stinking is not difficult, but if you avoid cleaning sweaty sandals, no matter which brand, the odour will return. Cleaning Keen sandals is exceptionally easy--and it doesn't matter which design of Keen sandal you own. Washing instructions for both the synthetic and leather upper sandals is the same.
Place the sandals on a flat surface. Sprinkle and cover the insoles with baking soda. Leave it overnight, undisturbed.
Shake out the excess baking soda. Place the sandals in your washing machine.
Set the machine to a cold water, gentle cycle. Add just a teaspoon of mild washing powder and let the sandals go through a wash and rinse cycle.
Place the sandals in a well-ventilated area, in front of a fan, to air dry. If any odour remains after washing (it shouldn't), sprinkle baking soda on the insole and leave over night before shaking the sandal to remove excess baking soda.
Wash your sandals once a month if you wear them daily. Always let the sandals dry completely before you wear them. After washing and drying sandals with leather uppers, condition the leather parts with a leather conditioner to keep these parts supple. Use deodorising foot powder on your feet before slipping into your sandals--this will keep the shoes, and your feet, fresher much longer. If you wear socks with these sandals, change your socks if they become damp. Damp socks get smelly fast and this odour will transfer to the sandal.
Keenfootwear.com advises against putting sandals in the dryer (see ref.).