There are a lot of vitamin waters that have zero calories, too. Like Sobe water zero. I imagine the Crystal Light is way more economical, though.
My philosophy about diet foods is more around portion control. Diet foods can be so depressing, for example, tasteless boiled chicken or fish with tasteless vegetables that I don't like anyway. Salad with lemon juice? Lord, take me now. I keep weight in control by eating what I like, just not much of it. And no sugar at all, anywhere.