Bottled water is acidic. Check out many videos on YouTube which will show you what is this industry does. In my personal water testing Fiji water was alkaline, rest were acidic. I also have done test on various types of water, filtered, boiled, distilled, etc. a few years ago. You can search for it on this forum.
To keep your breath fresh it can be, use a tongue scraper, no other substance should go in your mouth, but water.