In a medium saucepan, combine 3 cups of water with the sugar. Bring to a boil over medium heat and stir until the sugar dissolves. Remove from heat, set aside, and let cool slightly.
Heat the remaining 1 cup of water until it boils. Pour the boiling water over the tea bags in a mug and let them steep for about 5 minutes. Remove and discard the tea bags.
In a large freezer-safe container, combine the cooled sugar water, the brewed tea, the thawed orange juice concentrate, the thawed lemonade concentrate, and the brandy. Stir well to blend the flavors.
Cover the container and freeze the mixture for at least 8 hours or overnight until slushy. To serve, scoop a portion of the frozen mixture into a glass halfway and top with lemon-lime soda. Stir gently before enjoying and garnish with an orange slice.