Use the plunger
Remove any plug or sieve that may already be in the sink. If there is an overflow opening in the sink, cover it with a piece of cloth. You do not want any additional airflow when using the plunger.
Run enough water into the sink to completely cover the rubber cup of the plunger. Then place the plunger cup over the drain, slightly tilting the cup to get rid of any air trapped inside the pipe.
Pump the plunger up and down. Do this up to 10 times. This will cause water trapped in the drain to emerge. With the emergence of water, it must cause any obstruction in the drain to dissolve and disperse.
At the last blow, abruptly pull the plunger out of the water. This final move must cause the water to run away.
The work of the Trap
When you look under your sink, you should see an “S” tube-shaped section. This is known as the goose neck “trap.” Place a bucket under this gooseneck trap.
At the bottom of the trap is a cleaning plug. With a wrench, unscrew the cap from the bottom of the trap and drain any water that might be out.
Using either a gloved hand or a folded wire hook, clean the stop. Then simply replace the cap.