Bring 2 cups of water to a boil in a medium saucepan or kettle. Remove from heat and add the 4 black tea bags. Let steep for 5 minutes, then remove and discard the tea bags, gently pressing them against the side of the pan to extract extra flavor.

While the tea is still hot, add 2 cups granulated sugar. Stir until completely dissolved and no sugar grains remain. Let the mixture cool for about 10–15 minutes until warm but not piping hot.

In a large mixing bowl or stock pot, combine the warm tea-sugar mixture, thawed orange juice concentrate, thawed lemonade concentrate, brandy, and 4 cups room-temperature water. Whisk or stir well until fully combined and smooth, with no streaks of concentrate.

Pour the mixture into a large freezer-safe container (about 4 quarts), such as a 9×13-inch freezer-safe pan, an ice cream bucket, or a large plastic container with a tight-fitting lid. Cover and freeze for at least 8 hours, preferably overnight or up to 24 hours, until slushy. The mixture will not freeze rock solid because of the alcohol.

When ready to serve, let the container sit at room temperature for 10–15 minutes if very firm. Use a large spoon or ice cream scoop to fill each glass half to two-thirds full with the slush. Top with chilled lemon-lime soda, ginger ale, or lemon-flavored sparkling water. Stir gently to combine and garnish with orange slices, lemon slices, and/or a cherry if desired.