While your oak dining table seems like a good place for a kid to set that glass of lemonade, it's not so good when he leaves the room and forgets about it. The outside of the drink "sweats," dripping down onto the wood and ultimately leaving a white ring from water damaging the finish. Rather than panicking that the entire table may need to be refinished, you can remove that white ring with household materials, especially if you act quickly.
Blot moisture from the damaged area using paper towels, if the ring is fresh. If the damage occurred in the past 24 hours, moisture is still likely present in the water ring. Blow a stream of hot air from a hair dryer on a low setting over the water ring. In some cases, the air is enough to remove the moisture from the table, making the white marks disappear.
Wrap a clean, soft cloth around your finger. Spoon a small amount of mayonnaise onto the cloth and rub it over the white mark. Leave the mayonnaise in place for a minute or two, and then wipe it away with a damp paper towel, drying the area immediately with a clean cloth. If the stain is still visible, reapply mayonnaise and let it sit for an hour, again wiping away with a damp paper towel followed by a dry cloth.
Create a paste by pouring a small amount of baking soda into a shallow bowl, adding just enough water to achieve a paste-like consistency. Dip a soft cloth wrapped around your finger into the paste, and then rub the paste over the damaged area, following the direction of the wood grain. Rub until the stain disappears. Wipe with a damp paper towel, followed by a dry cloth.
Pour a small amount of olive oil into a shallow bowl, followed by an equal amount of vinegar. Whisk them together with a spoon. Dip a cloth into the solution and rub it over the water rings, working with the grain. Buff the area with a clean, soft cloth.
Dip your finger into petroleum jelly, and rub it over the water rings, coating the area completely. Wipe the petroleum jelly away after 12 or more hours, using a clean, soft cloth.