You can’t make sweet tea by stirring sugar into a glass of unsweetened tea.
You need a small saucepan to boil the water and steep the tea. It will probably be a battered-looking, well-used pan reserved exclusively for the task. To make a half-gallon pitcher (yes, there is usually a certain pitcher that is always used for tea and nothing else), heat about 2-3 cups water to boiling (some say a pinch of baking soda or a dash of salt will make the tea smooth-don’t worry about that if you like just a little kick), remove from heat, then put in 6-8 regular tea bags (or 2 family-size) with the tags hanging over the side of the pan. Steep tea until it is very dark. In the meantime, dump a cup of sugar, more or less (some actually use a cup and a half!), into the pitcher. When ready, pour the steeped tea over the sugar. Stir until the sugar is dissolved. Add cold water to fill the pitcher and stir to mix.
You can refrigerate the tea before serving, but I like to pour the still-warm tea into a tall glass full of ice and enjoy that first sip as a warm-cold mix before swirling the glass to make the tea icy cold all through.
Just remember, never drink sweet tea through a straw. Do enjoy sweet tea year-round, but especially in the summertime. Every day.