Sweat is naturally odorless, but makes a good environment for some bacteria to grow and produce off-smelling substances. These bacteria are naturally present on our skin. Therefore, more odor is caused by factors causing more sweating, such as wearing shoes and socks. Less ventilation boosts feet smelling more (wearing shoes and socks).
Washing feet and applying the sodium bicarbonate daily is a very effective and cheap way to prevent foot odor, and swabbing feet morning & evening daily with isoprophyl alcohol for about two weeks also a good remedy.
Foot odor depend on environment, habits and genetics of an individual.