Cut pork into ½ thick x 1-inch wide x 1 ½ inch long pieces.
In a large bowl combine soy sauce, garlic, onion, juice of 2 lemons, 7-UP, ground black pepper, dark brown sugar and ketchup.
Whisk mixture to dissolve ingredients well and pour marinade mixture onto the pork.
Cover and set in the fridge overnight or at least 4 hours before grilling.
Soak bamboo skewers in water for at least 30 minutes before putting meat on.
Slide pork onto skewers and set aside.
Grill on direct heat until pork is done, turning as needed to obtain char marks on both sides. (about 10-15 minutes)