Overhydration, but I'm not sure whether a sedentary person drinking it orally is at risk for that. (We know runners drinking hydration fluid and sedentary people taking hydration intravenously are at risk).

Empty calories, but you can offset that.

Excess salt (but it is now uncertain as to whether excess salt is harmful in the absence of high blood pressure).

It's also weird, as in it's both an evolutionary novel and culturally novel thing for you to do, and that means it's risky until proven innocent.