Some cats seem to smell bad, and others do not.
I have three cats and only one smells bad (it’s the male, by the way!).
Some cats dig around in the litter more than others — an obvious reason why your cat may smell bad.
If your cat is not grooming himself often, he may smell worse than if he did groom himself. If your cat’s breath is bad, grooming may have the opposite effect. He could simply be spreading his bad breath all over his fur. You may be interested in reading more about why your cat has bad breath.
If bathing your cat is not an option, you could consider a variety of waterless bathing products. Recently, I have tried Furminator Waterless Deshedding Shampoo Conditioner, and Pet Head Waterless Shampoo.
The furminator product has a fresh scent that is strong enough to make the cat smell nice, but not too strong (in my opinion anyways). The Pet Head product has a very strong blueberry scent. I like the smell of it, but I’m not sure if the cat does.
As you can see, kitty still doesn’t look too impressed with this waterless form of bathing: