I grew up eating these skewers as a kid at almost every Filipino party I attended. They remind me of my childhood.
Technique tips: The sugar from Sprite helps tenderize and caramelize the chicken.
Swap options: If you can't find banana ketchup you can use regular ketchup instead.
Combine soy sauce, banana ketchup, pepper, Sprite, lemon juice, garlic, ginger, sugar, and salt in a bowl; add chicken and toss to combine. Cover and refrigerate overnight.
Thread chicken onto skewers (reserving marinade) and brush with oil. Heat grill (or grill pan) and cook, turning as needed and brushing with reserved marinade, until charred and cooked through, about 12 minutes. Transfer to a serving platter and garnish with scallions and crispy garlic.