Toothpaste can be used to remove water stains from varnished wood. However, if the toothpaste has dried on the wood it will leave a white residue. You can clean this off by polishing it using a wood cleaner. If a wood cleaner is not available, you can easily make an all-natural one with items from your kitchen.
Pour 1/4 cup of the olive oil into a spray bottle. Add 2 tsp. of lemon juice to the olive oil and mix with a spoon.
Spray the cleaning mixture onto the surface of the varnished wood. Allow the mixture to sit on the stain for at least two minutes.
Rub a clean cloth over the toothpaste stain in a circular motion. Wipe the surface of the varnished wood with a second clean cloth.