Combine vinegar, garlic, whole peppercorn, and salt in a bowl. Stir.
In a deep wide plate, pour-in the mixture and then lay down the fish in a manner that the sliced part is facing down (skin should face up). Cover and place in the fridge. Marinate for 8 to 12 hours.
Heat the cooking oil in a pan. Fry both sides of the bangus in medium heat until the color turns medium brown (note: it should take around 5 minutes per side). Note: the oil has a tendency to splatter because of the liquid from the marinade. Make sure to cover the pan while leaving open a small space for the steam to escape.
Serve with spiced vinegar (sinamak).
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