Put a thick towel on top of the water ring on your coffee table.
Turn your iron on a dry, low or medium setting and let it warm up.
Put the iron on top of the thick towel on your coffee table, and leave it there for about ten seconds. This will loosen the water mark and transfer some of the moisture to the towel.
Create a cleaning solution of one teaspoon of water and one tablespoon of baking soda. This will create a paste.
Lift the towel from your coffee table and apply the paste directly to the remaining water ring stain. Use a cloth to massage the paste into the stain using circular motions.
Wipe away the cleaning solution and check the water ring. If you can still see it faintly, make a new cleaning solution out of equal parts of olive oil and vinegar.
Apply a small amount of the vinegar and olive oil solution to the water ring, and use a cloth to scrub the stain gently, going with the grain of your coffee table.
Get a new cloth and buff the coffee table until it is dry. The olive oil will leave a nice shine.