Combine the brown sugar and water in a small saucepan and heat gently over low heat, stirring just until the sugar fully dissolves; do not boil. Remove from heat, add the orange zest, lemon zest, cover, and let steep for about 10 minutes, then strain and allow the syrup to cool completely.
Add the orange pulp to a large pitcher and gently muddle it just enough to release juice and light texture without turning it into purée.
Pour the cooled citrus syrup into the pitcher with the orange pulp, add the pineapple juice, orange juice, and fine sea salt, and stir to combine. Add the ice-cold water and mix gently until fully integrated and uniform.
Refrigerate for 1–2 hours until fully cold and flavors are integrated, stirring once before serving.
Fill glasses with ice, pour over the pineapple orange drink, and garnish with orange slices and fresh pineapple slices.
