LOL! Maybe he eats way too much meat? Red meat makes it taste and smell stronger. Tell him to stay away from the burgers. Also, maybe he just needs to wash it! Tell him to wash before doing the deed...use an antibacterial body wash or saop bar.
It is def. something he ate. A while back i had garlic like 4 times in a week and i garlic smell was coming from every pore in my body for a week. One day i drank about 40 oz. of water and it went away. tell him to drink some water to flush his system out...if that doesn't work...its something on the outside..tell him to shower