1. In a blender, combine pineapple juice, garlic, chili powder, cumin, oregano, salt, and white vinegar. Blend until smooth.
2. Place chicken thighs in a large bowl or ziplock bag. Pour marinade over the chicken, ensuring all pieces are well coated. Marinate for at least 1 hour, preferably overnight.
3. Preheat grill to medium-high heat. Grill chicken for 5-7 minutes on each side, until fully cooked and slightly charred.
4. While the chicken is grilling, grill the pineapple and onion until they are slightly charred.
5. Serve the chicken with grilled pineapple and onion. Enjoy!