Foot skin is very different from the normal body skin... The sole aspect has a thick glaborous skin which has much more layers of cells than normal skin. Usually it won't sweat as much as it does in between the toes and on the upper part of the foot... If it's sweating so much as u say then definitely it might be a condition which we call hyperhidrosis... It can be treated by medications which will decrease the sweating and hence the foul smelling..
Next Steps
Consult a doctor, preferably a podiatrist, for proper advice and proceed..
Health Tips
Proper foot care and check up for any infections in between the fingers is essential..