It is important to get enough plain water for the body to function well. Carbonated water contains carbon dioxide and you can tell from the name that it is something that is acidic (by adding carbon dioxide), so avoid it if you want to invest in your health.
When you feel thirsty, it has often already gone too far. The body has started to dry out. That’s why it’s good to replenish water regularly, not just when you’re thirsty.
"Pure Water is the World's First and Foremost Medicine". - Slovakian Proverb