The Best Way to Clean a Composite Granite Sink Is by Using a Mixture of Vinegar and Baking Soda. the Mixture Will Break Down the Residue Built Over Time, and Then the Sink Can Be Rinsed Off with Warm Water.
If You Are Unable to Use This Solution, You May Need to Scrub the Sink with A Brush or Cloth and Then Rinse It Again with Warm Water.