current RV always had a smell when we first used the Hot Water.
Never had that problem on any of the previous RV's
Based on her research my wife insisted it is the anode and the water heater needed to be flushed..
Since the wife is in charge I just do what the captain orders whether I agree or not as I never win that argument.
I did it.. swapped out a good anode for a brand new good anode.

flushed tank with some peroxide and that wand Ctech was talking about.
all I can say is it helped, but it still gets a funny smell after a long sit and first use of hot water.
I generally drain the water heater and the fresh water tanks anyway.. on a regular basis.
doesn't seem to make sense to leave water in it..
worth mentioning friend of mine paid 1400 dollars to have his water heater replaced in his 6 year old Montana..
so if draining the water heater and cleaning it out helps extend the life, go for it.