Shirley (mid-west, Missouri) on 07/21/2007:

A word of caution, vinegar can remove the enamel from their teeth, the same as it does for people. I have always added 1/8th teaspoon of baking soda to one-teaspoon vinegar before I add it to their water. Let the vinegar/baking soda mix sit until the fizz stops then add it to the water.

I could have missed it but I didn't see anyone saying they were doing that mix. We don't want to fix one problem while causing another.