5 cups large-dice pineapple (from 1 large pineapple, about 5 pounds)
1/2 cup packed light brown sugar
1/2 cup white wine vinegar
1/4 cup soy sauce
2 medium garlic cloves
1/8 teaspoon cayenne pepper
36 extra-large shrimp (about 2 pounds), peeled and deveined
12 (10-inch) metal or wooden skewers
Combine 2 cups of the pineapple, the sugar, vinegar, soy sauce, and garlic in a blender and blend on high until smooth, about 30 seconds. Pour into a medium saucepan and bring to a boil over medium heat.
Skim off any foam and reduce heat to low. Simmer until glaze is thick and syrupy enough to coat the back of a spoon and has reduced to about 3/4 cup, about 30 minutes. Stir in cayenne and set aside to cool slightly, at least 5 minutes. Meanwhile, heat a gas or charcoal grill to high (about 400°F) or a grill pan over high heat until very hot.
Skewer 1 shrimp, making sure to pass the skewer through the thick portion and the tail portion, then skewer 1 piece of the remaining pineapple. Repeat, alternating between the two and leaving no space in between, until you have 3 shrimp and 2 pineapple pieces per skewer. Brush the skewers on one side with the glaze.
Rub the grill with a towel dipped in vegetable oil, place the skewers on the grill glaze side down, and brush the other side of the skewers with more glaze. Continue brushing and turning every few minutes until the thick portions of the shrimp are white and firm, about 15 to 20 minutes. Remove from the grill and serve immediately.