In a large bowl, whisk together the banana ketchup, calamansi juice (or lemon lime soda), garlic, soy sauce, salt, pepper.
Add the pork belly strips to the marinade, cover, and refrigerate for at least one hour and up to overnight.
Preheat grill to medium-high heat.
Add the pork belly and grill for 6-8 minutes on each side.
While the pork belly is grilling on the first side, pour the marinade into a small saucepan and bring to a boil on the stovetop. Allow to boil, stirring, for 4-5 minutes. Baste the pork with the cooked marinade sauce after flipping the meat over to the other side.