Heat the olive oil in a saucepan over low heat. Saute the garlic for 1 minute while stirring.
Add the pineapple juice, apple cider vinegar, soy sauce, brown sugar, and ketchup. Bring the mixture to a boil while stirring to dissolve the sugar.
Once the sugar is dissolved, reduce to a gentle boil. Mix the cornstarch and water together and whisk it into the saucepan. Continue cooking on a gentle boil until thickened. This will only take 1-2 minutes.
Notes
If you prefer, you can addHoisin sauce instead of Ketchup. which is very often referred to as Chinese ketchup.
The brown sugar can be replaced with honey or agave; however, the taste will be slightly altered.
Store the sauce in an airtight container in the refrigerator for up to 2 weeks or freeze for up to 2 months.