Whiskey.
LOL, I'm kidding. Don't mind me, I'm in a goofy mood today. Which doesn't happen very often.
I was going to suggest the Koolaid singles, but you said you weren't a fan of Crystal Light, so I don't know how big that suggestion would go over. I've tried protein drinks in the past, but they're just too many calories for me and I don't like to drink my calories. You asked if protein drinks work. Not sure what you mean by that. Do they work what? In weight loss? Or..... something else?
If you meant weight loss, everything can work in weight loss, it's just a matter of how many calories you take in.
I really can't think of anything that's 'healthy', except maybe carrot juice. I love carrot juice, but again, we're getting into the whole juice thing.
Me, I'm perfectly happy with drinking water all day long, but if I want flavor, I just go grab a Koolaid single and dump it into my water. Sorry, but that's about all I can suggest. Maybe someone else will chime in with some better ideas