In a small bowl, whisk together cornstarch and water. Set aside

In a medium saucepan, combine pineapple juice, rice vinegar, brown sugar, ketchup, and soy sauce and bring to a boil over medium heat. Stir in cornstarch slurry and cook until thickened, about 1 to 2 minutes. Remove from heat and use immediately or store in an airtight container in the refrigerator for up to 2 weeks.