Typically, if a dog has bad breath, it is because of a dental problem. Having a dental done will help you start from a clean slate, and then you can focus on good oral habits. Teeth brushing, CET rinse, raw meaty bones, etc., etc.
Cynder has bad breath and it isn't because of her teeth, but because of her underlying esophagus issue. So if the breath is absolutely disgusting, definitely look in to an underlying cause and don't just assume it is "dog breath".