yeah...i'm a coffee slave there...
the unfortunate thing about the green tea frappuccino is just that--it's a frappuccino. which means it's made with the same loaded-calorie cream base as all the other non-coffee frappuccinos. we do use a starbucks matcha tea to make it, but i'm not a fan of it--extremely vegetal taste when used on its own. that's why the recipe calls for adding the honeydew melon syrup, which is all i can personally taste in the green tea frappuccinos.
if you don't like the calories/additives of frappuccinos, though, you can trust the iced green tea and the green tea lemonades. sweetened, the barista will add a couple of pumps of unflavored syrup, but if you ask for it unsweetened, you get our plain, brewed-to-ice tazo zen green tea. you can get the green tea lemonades unsweetened too, but of course there will be the natural sweetener of the lemonade, which is about one part to the two parts tea, and the lemonade starbucks uses has only natural sugars, i think.
to make it short: starbucks will never have a healthy frappuccino. go for the iced tea.