It never fails, even though you have coasters out for your guests someone’s  sweaty drink perspires all over your wood furniture! To erase these marks soak a rag in rubbing alcohol. Wring it out and then lightly dab the stain until it disappears. DO NOT scrub vigorously!! This will work because the rubbing alcohol will penetrate the damaged varnish and then quickly evaporate dissolving the water stains. If you have scratches or other types of blemishes on wood furniture, use a walnut (shell removed!) to rub them out. The walnut’s natural oils will darken the marks in seconds!