Pills wont work. Probiotics are for your bowels, not beath. Hygiene and food choice are your real solutions. Brush and floss (correct technique, ask dentist) each morning and night. Reduce your sweets & refined carbs (chips, soda, cookies, bread, gravy, etc), eat more vegetables and whole grains like brown rice. If no improvement after a week, see your doctor to rule out other medical causes.
4 weeks. Bad breath or halitosis is often caused by sulfur causing bacterial growth in the mouth. Good brushing of the teeth, gums and tongue cane reduce this. Probiotics work more slowly to reestablish a more "natural" balance of helpful bacteria in the GI tract. Avoiding smoking, coffee, and tea may also help.