01 - Combine sugar and water in a small saucepan. Heat over medium heat, stirring continuously until sugar completely dissolves. Remove from heat and allow to cool to room temperature.
02 - Whisk together cooled simple syrup, pink grapefruit juice, grapefruit zest, and lemon juice in a large bowl or pitcher until thoroughly combined.
03 - Pour mixture into ice cream maker and churn according to manufacturer instructions until reaching soft-serve consistency, typically 20–25 minutes.
04 - Transfer sorbet to freezer-safe container, cover tightly, and freeze for 4–6 hours until firm texture is achieved.
05 - Scoop sorbet into individual bowls or glasses. Top each serving with 2 fresh basil leaves and serve immediately.