Don't most commercial alcoholic teas use high proof alcohol mixed with tea flavoring and sugar? I don't know that they actually ferment anything containing tea? So if you are trying to make a twisted tea, I would probably follow that methodology, ferment something as neutrally as possible, highly fermentable sugars, (perhaps some dextrine to add extra sweetness?) clean yeast strain, maybe semi lager it to make it crisp as possible, no hops etc. And then after it is done fermenting, brew up some really strong tea, and mix the two, add some priming sugar, and let it carbonate. And if you want the really sweet stuff, you might have to do something to the alcoholic side of the brew to kill off the yeast, like pasturising it, then adding the tea and a bunch of sugar then force carbonate it. If you don't de-activate the yeast, I imagine you would have gushers all over the place if you made it as sweet as the commercial versions I have tried. Anyhow, good luck, and have fun!
O, guid ale comes, and guid ale goes,
Guid ale gars me sell my hose,
Sell my hose, and pawn my shoon -
Guid ale keeps my heart aboon! -- Robert Burns