There is some unpalatable concoction served as "sweet tea" in various chain sit-down restaurants in the greater deep south area that I assume either uses some non-sugar sweetener or some instant tea mix. I now order unsweetened iced tea, and add sugar to taste. see also: "If this is tea bring me coffee, and if it is coffee bring me tea." https://quoteinvestigator.com/2015/11/11/coffee-tea/
You put the sugar in when the tea is hot because it allows you to super saturate the room temperature/cold tea with sugar and the tea is more like a syrup. If you just stir in sugar, you can't get the same amount, especially if they bring you chilled tea.
You can practically feel the diabetes when you drink sweet tea in the south.