Sometimes the smell isn’t from the water at all—it’s from the drain itself. Bacteria can grow in your sink’s P-trap, especially if you don’t use that sink often. Pour a cup of baking soda, then a cup of vinegar, let it fizz for 15 minutes, and flush with hot water.
If that doesn’t work, you might have a dry trap (common in guest bathrooms). Just run the water for a minute to refill the seal. I swear, 80% of “sulfur smell” problems are actually just stinky drains.
