Hot water only ‘sulfur’ odor is (usually) a product of sulfate, iron and/or manganese reducing bacteria. Another cause is a trace amount if H2S in the cold water. To establish if that is the case, spray water into a 5 gallon bucket as you hang your nose on the rim smelling for sulfur. If there is a sulfur odor, a sulfur filter would remove it.
If it is bacteria related you can remove or replace the anode rod with an aluminum rod or set the temp of the heater to 140f which will kill the bacteria that use the usually magnesium rod as a food source and produce H2S. You can also drain and then flush the heater and sanitize it with bleach. That doesn’t always work as a permanent soultion though. The use of water treatment is limited by the type of bacteria causing the odor and identifying the type is difficult. The use of any disenfectant in a sloution feeder or a pellet dropper mounted on the well is an option regardless of what type bacteria is present.
Water treatment dealers are the best chooice for identifying and solving the problem. Removal of an anode rod usually voids heater warranties.
Quality Water Associates