1. In a small saucepan, heat the vinegar and sugar over medium heat until the mixture boils and the sugar dissolves. Add the mango jam, barbecue sauce and onion and bring it to a boil. Remove from heat. Season with salt and pepper to taste.
2. Preheat the grill to medium-high.
3. Thread the shrimp onto the skewers. Sprinkle the shrimp with salt and pepper and drizzle with olive oil.
4. Place the shrimp skewers on the grill and cook for about 3 to 5 minutes per side, depending on the size of the shrimp, until the shrimp are opaque and cooked through.
5. Place the shrimp on a serving platter and brush them with the mango-barbecue glaze.
Please note that some ingredients and brands may not be available in every store.