Usually I just go to Costco (or any other grocery store), pick a flavor I like and check ingredients. So I can't really say what brands I like.

Why not make your own tea then? It's not too complicated, it takes more planning then powder but it's not too bad. I have a tea maker and it goes pretty quickly, and then from there you'd just have to ice it. Tea brands I like are Stash, Revolution or Yogi Tea if I'm going for something bagged. If I want a loose tea I get something from Teavana, they have both shops and an online store. I recommend the shops if there is one near you because you can sample different teas and create your own blends.