Being in the South married to a man who loves his sweet tea, and making sweet tea at least a few times every week, I can add a bit.
The basic recipe I was taught was: 1 cup sugar, 2 Luzianne tea bags, hot water. In a pitcher, I believe two gallons of water.
Those who like their sweet tea like it sickly sweet (in my opinion). This or more sugar is true sweet tea.
Over time, I've managed to adjust the recipe. First, since he was having trouble sleeping, I reduced the caffeine. I now use one decaf bag and one green tea bag (still both Luzianne).
Also, I was able to reduce sugar so now I put about 1/4 cup of sugar and 28 drops of Lakanto monkfruit. According to my husband, not quite as good as the real stuff, but it's a fair substitute for the cup of sugar and drinking less sugar has definitely improved his health and sleep.
(And I think the Luzianne are special tea bags specifically for sweet tea. Others can be used, of course, but I think a Luzianne tea bag is a little bigger than a regular teabag I'd use to make green tea.)