Brushing may clean your teeth, but it only masks bad breath, since the problem really lies within your throat and tongue. When the bacteria in your mouth lose access to oxygen (which happens when you use alcohol-based mouthwashes, take certain prescription medications or simply sit with your mouth shut for a long time), they emit sulfur compounds that smell like death. Neutralize them by drinking more water throughout the day and eating oxygen-rich vegetables, like parsley and celery.