1. Mix sugar with 1 cup water in a small saucepan. Strip leaves from three-quarters of thyme and add leaves to sugar mixture. Heat over medium heat, stirring often, until sugar dissolves, about 5 minutes. Strain into a large pitcher.
2. Juice 11 tangerines and add juice to pitcher. Add ice and 8 cups water.
3. Slice 2 tangerines thinly, removing seeds, and add to pitcher with remaining quarter bunch of thyme sprigs.