Can lupus give you bad breath?

Don't need lupus for. Causes can include diet, e.g. Onions, garlic, coffee, etc., sinus issues, dental problems, some GI problems, meds, supplements. Lupus is not known for causing bad breath, but arguably could if affects salivation, etc.
Possibly. Who knows? When tissue does these strange things, anything, including bacterial invasion, can happen. Have your dermatologist check it out.