In a medium bowl, combine crushed garlic, sliced onion, salt, black pepper, and vinegar, stirring well to create a flavorful marinade.

Place the cleaned and butterflied bangus skin side down in a shallow dish and generously pour the marinade over it. Cover the dish with plastic wrap and refrigerate for at least 4 hours.

Once marinated, carefully remove the bangus and pat it dry with paper towels to remove excess liquid.

In a frying pan, heat enough cooking oil over medium heat until it reaches about 350°F (175°C).

Place the bangus in the hot oil skin side down, frying for about 5-7 minutes until the skin turns golden brown, then flip and fry the flesh side for another 3-5 minutes.

Transfer the crispy Daing na Bangus to a plate lined with paper towels to absorb excess oil. Serve hot.