Is this just the hot water or all water in the coach. Are you in Florida or Mass?
If in Florida, run a cup of water from the faucet on the power pole and take a sip and smell. Lots of places in Florida have what is known as "Sulphur water" and it is just the nature of the water and not much can be done except to resort to bottled water (yuk) for drinking and cooking, or adapt to the Sulphur water as many Floidians have and actually enjoy it. The above mentioned remedies will help if it not Sulphur water. A suburban water will have the sacrificial anode rod that cause the water to taske bad when it needs replacing. If a Dometic water heater, they do not have an anode rod to blame, so multiple fills with mild bleach followed by a solution of baking soda will usually do the trick. Good luck with what ever route you take.