Chantix can cause mouth dryness, which can definitely contribute to bad breath. This side effect can be made better by chewing gum or sucking on sugarless candies. Regarding the change in your body fluid odor, it makes sense that since the medication is drying, that your body fluids would become more concentrated, therefore changing their odor. If it is a big problem for you, I would call your health care provider and discuss it with them.