There are two sources of "the smell". 1) bad water with sulfur in it 2) bacteria.
Mostly it's #2.
When the hot-water tank is left of some time, the O2 using bacteria use up all the O2 and dies off.
Then, since the O2 is all gone, the anaerobic bacteria can get going and break down the sulfur compounds naturally in the water, freeing the sulfur.
The solution is either is flush out the tank. a treatment of chlorine doesn't hurt
2008 F350SD V10 with an 2012 Arctic Fox 29-5E
When someone tells you to buy the same rig they own, listen, they might be right. When they tell you to buy a different rig then they own, really pay attention, they probably know something you don't.