In a medium saucepan, combine the pineapple juice, rice vinegar, brown sugar, ketchup, soy sauce, and water. Use a whisk to mix everything together until well combined.
Place the saucepan over medium heat. Stir the mixture occasionally as it heats up, ensuring the sugar dissolves completely.
In a small bowl, mix the cornstarch with a tablespoon of water until smooth. This will help thicken your sauce.
Once the sauce is hot, add the cornstarch slurry to the saucepan. Continue stirring while the sauce cooks for another 2-3 minutes, or until it reaches your desired thickness.
Taste your sweet and sour sauce and adjust the flavors as needed. You can add more brown sugar for sweetness or more vinegar for tanginess.
Remove the saucepan from the heat and let the sauce cool. Once cooled, transfer it to an airtight container and store it in the refrigerator for up to a week.
