I have used an excellent product by ProDen called "Plaque Off Animal". It gets rid of the tartar and plaque which causes bad breath. I just add a tiny scoop, which comes with the product, to your pet's food every day.
I have found that yogurt is the best thing for my dog. But you only can give a dog plain or vanilla, no other flavors. I give my dog a tablespoon every day and he loves it. Plus it is also good for their digestive system. I hope this helps.
This is a page about puppy with bad breath. Puppies can have very bad breath when they are quite young.
My dog got skunked last night and I used the hydrogen peroxide and baking soda and liquid soap method that worked very well on his coat. The problem now is that when the dog got sprayed by the skunk, he was barking and apparently got a mouthful of the spray also.