Personally I think fake sugars taste nasty.....

As far as green tea goes.... its not really meant to be served with sugar and IMHO doesn't need it at all as there are few bitter notes in a good green tea. I do generally prefer sugar with black teas. That said its difficult to find a mass produced iced green with no sugar added unless you have access to a natural food store or asian food store. If you like a sweeter tasting green tea try unsweetened jasmine green if you can find it. The jasmine flower brings a sweet note without needing sugar.