[mynameisnoone]

Not many. They're flavored water. Randos who lay down the tired bullshit Sodas all the same are morons who don't have a clue what they're talking about. The biggest negatives are likely the acidification due to the presence of carbonation interfering vitamin absorption and enamel erosion. A minor issue is the risks from potentially unsafe food colorings still found in many American beverages.

https://www.health.harvard.edu/staying-healthy/does-carbonat...