In a saucepan over medium-high heat, whisk together the 1 (6-ounce) can pineapple juice, ¼ cup rice vinegar, ½ cup brown sugar, ¼ cup ketchup, and 3 tablespoons soy sauce. Cook for 1-2 minutes, until the sugar is dissolved.
In a small bowl whisk together the 2 tablespoons water and 1 tablespoon cornstarch to make a slurry.
Add the cornstarch slurry to the saucepan and whisk it in. Bring the sauce to a simmer, then reduce to medium-low.
Continue cooking and whisking for about 5 minutes until it thickens slightly. Remove the sauce from heat and allow it to cool. Note that it will thicken more as it cools.
Video
Notes
Storage: Store the sauce in an airtight container in the fridge for up to 2 weeks. I don't recommend freezing this sauce.