A sulfur smell from the hot tank can be the result of a bacteria that thrives in dark places & warm water that creates the sulfide gas your smelling or it could also be from a natural high sulfur level in the water you last filled it with. Often a problem if the water is left to sit in an used tank during warm weather.
As others have said the tank should be cleaned out. Due to the design of most of our hot water tanks what ever may be in the bottom of the tank doesnt drain out. You could have yourself depending on where you have getting your water from a bunch of gunk in the bottom of the tank which can lead to the bacteria issue.
If you dont already have one a Hot Water Tank Rinser
is a good tool to have. Attach to your hose and stick the rinser with the little hook down towards the bottom of the tank and it will help clean out the bottom area of the tank of gunk. I am told that leaving gunk in the bottom of the tank will regrade the life of the tank, so its a good $6 investment if it helps your tank live a number of years longer.