Smelly sneakers are a common problem for people of all ages. Baking soda is widely regarded as an all-purpose odor absorber. Put the two together to eliminate odors from the sneakers. It's very easy to use baking soda to absorb those shoe odors without making a mess or even much of an effort. Just go to the pantry and follow these steps.
Loosen the laces on the smelly shoes so that you can lift the tongue up a bit. Raise the tongue enough so that it makes a little extra room inside the shoe, but not so much that it opens up gaps between the tongue and the shoe's lace eyelets.
Prepare some baking soda holders. If you have cheesecloth handy, lay down a triple layer that is roughly 6 inches square. Pour roughly 2 tablespoons of baking soda into the center, fold up the edges and secure them together with a rubber band. Make a second baking soda pod for the other shoe. If you don't have cheesecloth handy, just pour about two tablespoons of baking soda into any open container small enough to fit inside a shoe. This can be a small plastic food container, a deep beverage coaster or even a shot glass.
Put the shoes somewhere where they won't be kicked or disturbed for several hours. Set one dose of baking soda inside each shoe. Don't put it all the way down at the toe; keep it in the center where you made the extra room by lifting the tongue.
Tear off two small pieces of plastic wrap. Put one piece over the opening in each shoe. It doesn't have to be perfectly airtight, but the seal over the shoe will help the baking soda to be more effective.
Remove the plastic wrap and baking soda holders whenever you need to wear the shoes, but don't necessarily throw them away. You can put everything back in place when you're done wearing them if some odor still remains. The baking soda won't need to be replaced until you can actually smell the shoe odor in the baking soda after you remove it from the shoe.
If you don't have anything appropriate with which to hold the baking soda inside the shoes, you can always sprinkle some loosely inside the shoes and vacuum it out later with a vacuum cleaner's hose attachment. This method will often be more effective at absorbing odor because the baking soda is more loosely distributed, but it is messier.