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