In a small bowl, whisk together the water and corn starch to form a slurry. Set aside.
Into a medium pot, add the pineapple juice, ketchup, chili sauce, Worcestershire sauce, and garlic powder. Mix together until combined, then heat on medium heat until slightly thickened, about 10 minutes. Turn off the heat, then whisk in the slurry until well-dissolved
Transfer the pineapple BBQ sauce into an airtight jar and let cool. Store in the refrigerator until ready to use. ENJOY!