In a medium saucepan over medium heat, combine granulated sugar and water, stirring until dissolved, about 5 minutes.

Let the syrup cool to room temperature, approximately 15–20 minutes.

Blend watermelon, cooled syrup, fresh lime juice, coconut milk, and salt in a blender for 1–2 minutes until smooth.

Continue blending until no watermelon chunks remain for a creamy texture.

Strain the mixture through a fine-mesh sieve into a bowl to remove pulp.

Cover and refrigerate the strained mixture for at least 1 hour or up to 2 hours.

Churn the chilled mixture in an ice cream maker following manufacturer’s instructions for 20–25 minutes.

Transfer the sorbet to a freezer-safe container and freeze for at least 2 hours to set.