im pretty sure sodas are much worse for your health than cupcakes, doesn't it also deteriorate your bladder or something. And I'm almost certain diet drinks are generally worse, especially coke diet.
However in saying that, i buy a coke every morning at school, just because i hate coffee and i need a tasty caffeine injection, however I'm 17 and i don't really get hyper anymore (have you ever tried putting a heck lot of sugar into coke diet? Damn that was good stuff, it fizzes up like champaign).
But in my old school they allowed coke to anyone not in year 7+8 (first 2 years of secondary school, your like 11 around then), but they would just buy it off other people in the cafeteria, and i have to say, they go so hyper i have no idea how anyone can learn...
Trying to do my GCSEs with kids outside running around screaming as if they lost their head (i wish).
If all else fails, blame your Government.