Or you can apply some elbow grease and fix slow drains by cleaning out the drain and trap  – the U-shaped pipe that’s directly under the sink. Position a bucket under the trap to catch falling water and gunk and keep a pile of rags at hand for cleaning up. This can be a messy job – you may also want to wear rubber gloves.
Loosen and remove the couplings that hold the trap to the straight pipes that run from the sink and to the sewer. You may need to use a plumber’s wrench. If the pipe is plugged, all kinds of messy stuff will fall into the bucket and must be removed from the trap. If possible, take the trap outside and shoot a stream of water from the hose through it. Rinse it out thoroughly. Use a snake or wire from a coat hanger to remove built-up debris from the pipes.