When I eat at places where I can fill my own iced tea, I fill it all the way up with unsweet and put one splash of sweet on top.
That one little splash of sweet makes the entire tea almost too sweet to drink. I can’t imagine filling it up with all sweet. My pancreas would probably jump out of my body.

Knock, knock.
Who’s there?
Dave’s pancreas.
Dave’s pancreas who?
Why hast thou forsaken me, Dave?