Try "Sneaker Balls" from DICK's SPORTING GOODS or DSW or SPORTS AUTHORITY. They are $5.00 for a pair and you drop them in the shoes when not wearing them. They work great.
Sneaker Balls are no puny little air fresheners - they're packed with the power to tackle the odors inside a sneaker, gym bag or locker, where the toughest, ugliest smells hang out. Each ball contains a fresh, clean scent and an odor blocker formulated to counteract the unpleasant odors caused by perspiration, lasting three months. Sneaker Balls also work in cars, clothes hampers, drawers, diaper bags, suitcases or anywhere odors are a problem.
Sneaker Balls arent like any other air fresheners. Theyre smaller, tougher and rounder. Why? Because they have to work in nasty little places where other air fresheners dont fit. They are the only air fresheners with the moxie to tackle the inside of a sneaker, gym bag or lockerwhere the ugly stuff grows! Sneaker Balls come in a variety of fun styles and fresh, clean scents and they contain TX-3, an odor counteractant that is specially formulated to block the unpleasant smell of human perspiration. Sneaker Balls also work in cars, clothes hampers, diaper bags or anywhere that odors are a problem. The scent lasts for 3 months. Just Twist to Activate The trademarked design of the Sneaker Ball features special scent windows that allow you to control the strength of the scent by opening them partially or completely.