“I’ve noticed that flavored carbonated waters have become very popular. Many are tasty and its feels like a healthy alternative for soda. Is there any concern about drinking them regularly, other than cost?”
The carbonation itself is not a problem. (See Is Carbonated Water Bad For You?) And as long as the beverages are not sweetened or artificially sweetened, there’s nothing to fear on that front.
The one potential fly in the ointment is that the fruit essences used to flavor the waters can be acidic enough to harm tooth enamel. An occasional glass is not a concern–especially as an alternative to soda. But sipping on flavored waters all day long could potentially do a number on your teeth.
Using a straw and rinsing your mouth with plain water (or chewing a piece of sugarless gum) after enjoying a glass of flavored water can help by quickly restoring the pH in your mouth to a more tooth-friendly level.