Sweet and Sour Sauce, Nora Daza inspired. For lumpia, fishball, etc.

This is one of the best sweet and sour sauces I've tried. Very simple.
This is sauce is based on Let's cook with Nora, New edition.
Always remember: Always serve with love.
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Ingredients:
1/4 cup white vinegar
1/4 cup brown or white sugar
1/2 tsp salt
1/2 cup water, add more to adjust thickness
1 tbsp cooking oil
2 tbsps tomato ketchup
2 tbsps cornstarch dispersed in 2 tbsps cold water
Optional (my modification):
1 clove garlic
Chili flakes
Instructions:
1. Combine vinegar, sugar, salt, and water in a bowl. Set aside.
2. Using a sauce pan, heat oil, and fry ketchup and black pepper for a minute.
3. Stir in the vinegar mixture, add garlic. Simmer until the vinegar reduces or the smell dissipates.
4. Pour in the cornstarch mixture.
5. Adjust thickness by adding water.
6. Dip your lumpia, shanghai, fishball, or kikiam.