I got Athlete's Foot while in the Air Force and had smelly feet for years until I was told about Boracic Acid Powder.
Later, this powder became unobtainable but you can buy BORAX (Trade Name) which is a water softener for laundry use and contains Boracic Acid.
Smelly feet is often caused by a fungus living in the skin which isn't affected by using loose powder so I dissolve 2 tablespoons of BORAX in a bowl of hot water, soak the feet in it for 15 minutes until the water goes cold and then leave the feet to dry naturally.
This ensures that the powder gets under the skin to the fungus.
It is now four years since I last used this method and my feet are still clean, fresh and normal.
Whilst I have not suffered any ill effects whatsoever from this treatment I would suggest that it is tested with care on a small area first as, what suits me may not suit you, and I do not wish to be held responsible for any ill effects which may occur.
More info on
http://www.tipking.co.uk/tip/3270.html
Borax is now extremely hard to find but a chemist may be able to order it for you.