A health and wellness writer for “The New York Times” just did an article on why you shouldn’t ONLY drink carbonated water.  Carbonated water IS just as hydrating as flat water.  The main problem is people who only drink fizzy water could mess up their TEETH. Unless you’re using tap water in a Sodastream, carbonated water doesn’t have fluoride in it like tap water does.  So it doesn’t protect your teeth.  But even with a Sodastream, the carbon dioxide in the bubbles lowers the pH in your mouth.  So your saliva is more acidic, and that’s bad for your enamel. Flat water is better for that. Fizzy water can also make you feel more bloated, and make acid reflux worse.