Well bad breath might indicate a health issue but if the cat is healthy then have you tried brushing her teeth? There are toothpastes and brushes developed especially for cats. I had the same problem and tried brushing....I'm not sure if there's another solution though like the "dental treats" I hope someone with better knowledge responds
Bad breath generally indicates a dental issue. First, take the cat to the vet to rule out any possible dental issue. If the vet doesn't find anything but recommends a dental cleaning, consider having it done. A thorough cleaning will improve the cat's breath. February is usually pet dental health month in the US and some vets offer discounts on dental procedures.
For at home treatment, brush the cat's teeth. Daily is ideal but once or twice a week is better than nothing if that's all your cat will allow. Use only pet toothpaste. Pet stores sell various brands of toothpaste and different sized toothbrushes and finger brushes. Here's a video of how to brush a cat's teeth: http://partnersah.vet.cornell.edu/pet-owners/cat-teeth
There are oral rinses you can use on your cat's teeth. Some you just squirt onto the teeth, others need to be gently rubbed on.
Additives that are put into the bowl of water are useless, IMO. Cats drink very little water so they're not going to drink enough for a water additive to have any effect on the teeth.
There are dental treats like Feline Greenies that you can try.
I prefer the CET brand of pet dental products. My cats love the poultry flavored toothpaste. I've used the CET dental treats before and they seem to work better than most treats. The treats are pretty large which a cat has to work on chew on to break up.
been super duper busy last month. awesome tips guys. I had "smeagol" checked and he was fine. My brother sent me a product he's been using and it worked as well. The name is Oxyfresh. I googled it and checked their site and was surprised they also have products for humans! how cool is that? haha. Just make sure you don't get mixed up and ending up using the one's for pets. hahaha.