usually feet will smell if there has been an accumulation of sweat which might allow some bacteria or foot fungus to grow. These small microorganisms sometimes release all sorts of compounds which ends up being the cause of the smelliness.
The approach to fix this situation is usually to always wear dry, clean socks if you can, and carefully wash one’s feet to ensure that dirt and sweat is properly washed away. If it is hard to access clean socks every single day, maybe letting them air out at night/turning them inside out will help them at least be dry. Also, ensuring that shoes aren’t too tight will minimise the excess sweating.