A good start would be your shoes. Do they allow enough air in for your feet to breathe? If not get a pair that does have vents. Socks are also a good addition. They help keep your feet dry so the bacteria does not grow as effectively. Dr. Scholl's or other foot bed insert for your shoe. They also help to absorb excess moisture. Topical creams for your feet. An anti-fungal would probably be the best. And a last ditch try is straight Baking Soda, not baking powder, in your shoe right before you put them on.
new shoes that you can clean, clean socks, good diet with lots of foods that have chlorophyll in it (green veggies), soak them in a foot bath daily, and if that doesn't work get checked by a doctor, you could have a medical problem.