In a small saucepan combine the brown sugar and water and heat gently over medium heat, stirring just until the sugar fully dissolves. Do not allow the mixture to boil — boiling dulls aromatic oils and creates cooked sweetness. Remove from heat, add the grapefruit peel strips and a pinch of fine sea salt, then cover and let steep for about 6–8 minutes. This short infusion builds structured bitterness without harsh pith extraction. Remove and discard the peel and allow the syrup to cool completely before using.

Spoon the fresh pink grapefruit pulp into a bowl, carefully removing any seeds. Lightly mash with a fork only a few times to release juice while keeping small juicy segments intact. The goal is controlled texture and freshness — not purée. This step creates a more cocktail-like mouthfeel rather than a thin juice profile.

In a large pitcher combine the mashed grapefruit pulp with about 80 ml of the cooled grapefruit peel syrup. Stir gently until evenly distributed. Taste deliberately — the mixture should feel bright, structured, lightly sweet, and clearly bitter. Adjust syrup gradually if needed.

Fill the pitcher generously with ice. Slowly pour in the chilled tonic water and stir once or twice only to integrate while preserving carbonation. Over-agitation will flatten the drink and reduce its refreshing bite.

Pour into ice-filled glasses and garnish with pink grapefruit peel twists. Serve right away while the drink remains lively, bitter-leaning, and texturally fresh.