The answer to 'my sink smells bad' is that the most common causes are food debris, grease buildup, or a clogged drain. This can lead to unpleasant odors coming from the sink. Symptoms may include a foul smell, slow draining, or even visible debris in the sink.
To address a smelly sink, you can try a few DIY solutions first. Use a drain cleaner or baking soda and vinegar to help break down the buildup. You can also try manually removing any visible debris or clogs. However, if the smell persists or you notice the sink is draining very slowly, it's best to call a professional plumber to properly inspect and clean the drain.