What can he do to prevent his penis from smelling bad, a type of soap? Or something else?

To prevent unpleasant odor in the genital area, it is important to maintain good hygiene practices. Daily washing with warm water and a mild soap, such as Dove for sensitive skin, is recommended. For uncircumcised individuals, gently retracting the foreskin to clean the area and removing any smegma buildup is important. It is also crucial to thoroughly dry the area to prevent moisture accumulation. If persistent odor is noticed, it is advisable to consult a doctor to rule out any underlying issues.