Tip: Alternatively, for a mocktail, substitute more ginger beer for gin.
Tip: For the simple syrup, mix equal parts of granulated sugar and water in saucepan; heat over medium heat just until mixture comes to a boil or sugar dissolves. Cool completely.
Infuse hot water with tea for 4 to 7 minutes; strain and cool to room temperature.
Add steeped tea, ginger beer, gin, simple syrup, grapefruit slices, and ice to large pitcher; stir to combine. Pour into 4 highball glasses.
Garnish with candied ginger (if using).