The "sulfur/rotten egg smell" is caused by a bacterial buildup in the stagnant water. It's easy to resolve, but unless you do the ENTIRE cleaning process, you won't kill the bacteria, so in a week, it'll be "right back to stinking"....
The process is in the water heater owner's manual. Essentially, drain the water heater, refill it and superchlorinate it, let it sit overnight (so the chlorine can kill the bacteria) then don't leave water in the water heater during storage. It's not the water heater, it's the quality of the water you're leaving in the tank.
If you don't have the water heater manual, here are links to both Suburban and Atwood. Page 7 for Suburban and page 5 for the Atwood.
http://techsupport.pdxrvwholesale.co...ser-Manual.pdf
https://www.gulfstreamcoach.com/medi...lon-Manual.pdf