May be it's due to fungal Infection

Body odor happens when your sweat meets the bacteria on the surface of your skin and makes an unpleasant smell. Sweating is your body's way of regulating temperature. While sweat itself is virtually odorless, bacteria use it as a breeding ground and multiply rapidly. Use a medicated antifungal powder and make sure to wear loose fitting clothes. Make sure clothes and undergarments r changed daily.