No real problem to them, except that I personally don't use crystal light since I consider it a processed product. Some people are also skittish about the artificial sweeteners, but I really don't have a problem with them.
I do drink lots of iced green tea though, a couple teabags in a pint of water set in the fridge for a few hours. It's hard for me to drink water straight unless I'm really thirsty. With tea though I have to be careful not to drink it around bed time, or else I'm wide awake for hours.