Combine sugar and 3 cups water in a non-reactive saucepan. Slowly heat until sugar melts. Remove from heat and cool.
Infuse the black tea in 1 quart of just boiled water for 2 minutes. Strain tea into a pitcher and then add 1 quart of room temperature water.
Combine the tea and the cooled simple syrup, mixing well. Refrigerate until cool.
To serve, fill a 12-ounce glass with ice cubes, a pinch of zest, and a sprig of mint. Add 2 ounces whiskey or bourbon and fill to the top with the sweetened tea. Stir and serve. Repeat as needed.