Partially freeze the meat for about an hour to make slicing easier.
Slice them thinly (about ¼-inch thick and 1½-inch wide) and across the grain. Keep them uniform in size, so they cook evenly.
Make the marinade by combining soy sauce, lemon or calamansi juice, lemon-lime soda, brown sugar, ketchup, garlic, and ground pepper. Taste and adjust as needed.
Marinate the meat and refrigerate for 2 to 8 hours.
Thread the meat on the skewers by bunching them together, creating folds like an accordion.
Over medium heat, cook leftover marinade for about 10 minutes to slightly thicken and prevent cross-contamination.
In an outdoor grill: Preheat to a medium-high temperature to get a nice sear. Cook them for about 5 minutes on each side. Brush the meat with basting sauce to keep them moist.
On the stovetop: Set your grill pan to medium-high heat. Brush the pan with oil and place the skewers once it gets very hot. Baste each side as you grill it for about 5 minutes.
In the oven: Preheat the oven to 400° F (200º C). Line a baking sheet with aluminum foil (for easy cleanup) and place a grill rack on top, if available. Arrange the skewers and bake for about 30 minutes. Flip them halfway through and brush them with basting sauce. Broil on high for 1-2 minutes toward the end.