Anyone that has worn a wetsuit before knows that it won't be long until it starts to stink. A combination of sweat, oils, and urine along with seawater, algae and whatever else you might have swam through make for a excellent breading ground for odor creating bacteria.
Daily cleaning care will help prevent most of the funky smells to start with. At the end of each day rinse your suit inside and out with fresh water. Hang your suit inside out on a heavy duty hanger, suits are heavy when wet not all hangers are up for the job. Let your suit hang dry and keep it out of direct sunlight if possible.
Cleaning with chemicals on a regular basis will vastly improve the smell. Don't use just anything, some cleaning agents are too harsh on the neoprene or if not rinsed fully can be irritating to your skin. Products such as Revivex Wetsuit shampoo or Reef Safe's Biodegradable Cleaner and Conditioner are best for removing salt, chlorine, sweat and smell while also conditioning the neoprene to help it keep its colour and stretch. Most of these cleaners are concentrated and need to be diluted for use. If you are in a pinch liquid dish soap will take care of the worst of the smell.
Storage of your suit is important. When stored for long periods of time folded or packed away neoprene will tend to get creased, musty and even moldy. Store your clean suit on a chunky wetsuit hanger in a cool, dry place and avoid keeping it in a garage with vehicles exhaust. Avoid using thin, wire hangers as they can cut through the delicate neoprene material or create a permanent crease and ruin your wesuit.
Don't forget about your neoprene accessories. Wetsuit boots, shoes, socks, gloves and hoods need care and cleaning too. Boots and gloves can get extra stinky since they are harder to air out. Accessory hangers can be a lifesaver for proper drying.