Peel, core, and slice the pineapple into even ¾-inch rings.
In a small bowl, mix the brown sugar, maple syrup, cinnamon, and vanilla until a thick glaze forms. Let it rest for 1 minute.
Preheat the grill to 350°F (medium heat).
Brush both sides of each pineapple ring generously with the glaze.
Place the pineapple directly on the grill grates.
Grill for 4–8 minutes per side, rotating halfway through each side for attractive grill marks.
Cook until the fruit becomes tender and develops deep golden caramelization.
Transfer the Grilled Pineapple with Brown Sugar to a serving platter.
Finish with a light sprinkle of coarse sea salt before serving.