Rejuvenate Garbage Disposal Cleaner & Drain Pipe Cleaner is the best drain cleaner and will also make a smelly sink smell wonderful. As a food waste disposer gets used the smelly drains and even worse drain gnats may become a problem. Rejuvenate uses bio-enzymatic foam that instantly eliminates grease, food, foul odors and dirty build-up on the disposer blades, walls and splash guards.