Dry rinse pork strips and drain well.
In a bowl, combine sprite, sugar, soy, chili peppers, vinegar, black pepper, garlic, and the 1 cup of only of oyster sauce. Add the pork and massage meat to fully incorporate. Marinate, turning meat once, in the refrigerator for at least 5 hours or overnight for best results.
In a bowl, combine remaining 1/2 cup of oyster sauce, ketchup and sesame oil. Set aside.
Thread 3 meat slices into each skewer. Grill meat over hot coals for about 3 minutes each side. When pork starts to lose its pink, baste with oyster sauce and ketchup mixture. Grill and baste, turning on sides, until meat is cooked through.
Remove from heat and serve as is or with spicy vinegar dip.