Snip up an old tee into squares, approximately 4 inches by 4 inches.
Dump a couple of teaspoons of baking soda into the middle of each square.
Grab the edges of the cloth and gather them together. Tie the gathered cloth off with ribbon or string to make a deodorizing sachet.
Stick one T-shirt sachet into each smelly shoe you have. Snag up the sachets and put them aside when you want to slip into your shoes.
Open up the shoe as much as you can. If it has laces and a tongue, loosen them so you expose the inner shoe sanctum.
Sprinkle a generous amount of baking soda into each stinky shoe. Pick the shoe up and tilt the toe downward to shift some baking soda to the toe area.
Let the inside of your kicks bask in the baking soda overnight. Turn the shoes over a trash can in the morning to get rid of the powder. Some of the residue will remain, but don't worry about it.
If you don't dump out the baking soda the next day -- no worries. Just do it before you wear your shoes the next time.
Repeated baking soda sprinkling into leather shoes can cause them to dry and crack. Try sachets instead.