Fill a microwave-safe bowl with apple cider vinegar and a few drops of dish soap. Microwave the bowl so the mixture becomes even more aromatic. Leave the bowl out uncovered as fruit fly bait. The soap will reduce the surface tension, causing any fruit fly that lands on the surface to drown.
Use vinegar plus baking soda, mix with water. Pour into those drains before sleep. Do it several days in a row. if still not working, you might have to call someone to water jet entir drainage.
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