Put one slice of lemon down the drain, and this common issue will be solved.

How to Use Lemon to Naturally Freshen Your Sink Drain
A comfortable living space requires regular cleaning and upkeep of a fragrant house. Odours and build-up may be particularly common in the kitchen because of frequent usage and food preparation. A typical problem is an unpleasant odor coming from the sink drain, which is often the result of limescale or organic matter buildup. You may successfully address this issue without resorting to harmful chemicals by employing a simple, all-natural solution: lemon.

Why Apply Lemon Juice?
An organic and natural way to get rid of bad smells coming from sink drains is to use lemons. Their strong acidity, which comes mostly from citric acid, aids in the breakdown of organic wastes and limescale, successfully getting rid of unpleasant odors. Here's how to clean your sink drain using lemons:

How to Clean the Drain in Your Sink:
Choose a Fresh Lemon:
Start by selecting a fresh lemon, which is a staple in most kitchens. Lemons are inexpensive and easily obtained.
Get the lemon slice ready:
Cut the lemon in thin, round slices. A thinner slice will release more citric acid effectively, so try not to make it too thick.
Take away the drain cover or grid that covers the sink drain hole to remove the drain cover. The lemon slice may now interact with the drain directly thanks to this procedure.
Put a slice of lemon over the drain.
Lay the wedge of freshly cut lemon immediately over the hole for the drain. Any accumulation that is producing the stench will be broken down by the lemon's citric acid.
Let the Lemon Do Its Work: