Boil water and pour it down the sink: The heat from the boiling water can help to break up any grease or food particles that may be causing the clog.

Use a plunger: Cover the drain with the plunger and pump it up and down several times to create suction and pressure that can help to break up the clog.

Use baking soda and vinegar: Mix 1/3 cup baking soda with 1/3 cup white vinegar in a measuring cup. Pour the mixture down the drain and let it sit for a few minutes before flushing it with hot water.

Use a snake or auger: This tool can be used to physically remove the clog from the drain. Insert the snake or auger into the drain and turn the handle to feed it into the pipe. 

Once it reaches the clog, turn the handle to break up and remove the blockage.

Call a plumber: If the above methods do not work, it may be time to call a plumbing company in singapore to repair the clogged sink.