The answer to 'sink foul smell' is that a smelly sink is often caused by a buildup of food, grease, or other debris in the drain. This can lead to bacterial growth and unpleasant odors. Common symptoms include a foul, rotten egg-like smell coming from the sink drain.
Some solutions to try first include using a plunger or drain snake to dislodge the clog, running hot water down the drain, or using a baking soda and vinegar solution to clean the drain. If the smell persists, you may need to remove the sink drain stopper or disassemble the p-trap under the sink to thoroughly clean out the pipes. For stubborn clogs or ongoing issues, it's best to call in a professional plumber to diagnose and resolve the problem.