Slice the pork into 1-inch-long pieces that are 1/2-inch thick using a sharp knife. Ensure to leave some fat on the meat to enhance flavor and tenderness.

In a large bowl, mix the sliced pork pieces with the minced garlic, soy sauce, ketchup, soda, calamansi (or lemon) juice, sesame oil, garlic powder, red pepper flakes, salt, and black pepper. Massage the marinade thoroughly into the meat. Place the marinated pork in a covered plastic container or a resealable large freezer bag and refrigerate overnight.

Clean the grill grates meticulously. Before lighting, spray a light coat of cooking spray on the grates to prevent sticking. Preheat the grill to medium-high heat for at least 10 to 15 minutes if using a gas grill.

Thread the marinated pork pieces onto skewers, placing about 5 pieces on each small wooden skewer (adjust if using larger skewers but avoid overcrowding). Ensure a fatty piece is placed on top for enhanced flavor.

Pour 1 cup of the marinade into a small saucepan. Simmer over medium-high heat for about 5 minutes. Add the brown sugar and mix thoroughly. Remove from heat and set aside.

Place the pork skewers directly on the preheated grill grates, lining them up side by side without overlapping. Brush the skewers with the sauce intermittently. Grill the pork for 3 to 4 minutes per side, using barbecue tongs to flip them, and continue basting with the sauce. The edges should be slightly charred, and the centers soft, juicy, and thoroughly cooked.

Serve the skewers immediately, either as an appetizer or as a main course with rice and achara on the side. Store leftover skewers covered in the refrigerator for up to 5 days or freeze them wrapped tightly in plastic wrap and foil for up to 1 month.