Honestly, you might not be getting the quality of sleep you need at your age (or any age for that matter).
Read these tips on improving the quality of your sleep...
http://www.sleepnet.com/tips.htmlMaybe that'll help you. But seriously, stay away from soft drinks, you're just setting yourself up for problems in the future. Drink lots of water.
And if it comes to it, and you can't help it, have a coffee but mix in some hot chocolate mix so that it tastes good.