This is a link to an interesting story about how even sugar-free beverages can promote tooth decay. The key take-away from this is to be aware of how acidic your food and drink can be, and how acidic (low-pH) drinks can promote enamel loss, leading over time to decay. These drinks include, among other things, dark colas (which often have phosphoric acid added), and most drinks that are citrus flavored — orange, lemon-lime, etc. Even otherwise “healthy” drinks, such as orange juice, can be a culprit. This doesn’t mean that you can never drink these beverages, it just means to be careful how often you do. Rinsing afterward with water is helpful.
As always, it pays to read the label!