Pour boiling water down the drain several times a day
Scrub the sink drain, stopper, and overflow holes with a brush
Clean the drain with baking soda and vinegar
Use an enzyme drain cleaner overnight
Remove and clean the P-trap if gnats persist
Fix any leaks or standing water under the sink
Keep the sink dry when not in use
Take out trash and food scraps regularly
Cover the drain when not in use
Set out apple cider vinegar traps near the sink
Replace old sponges, rags, and mop heads
Check nearby houseplants for fungus gnats
Seal cracks and gaps around pipes and cabinets
Call a plumber if the drain stays infested