Step 1

Mash ripe banana, tomato paste, vinegar, brown sugar, oil, ginger, onion powder, garlic powder, cayenne, salt, allspice, and turmeric together in a saucepan. Add water and stir to combine.

Step 2

Place over medium-high heat and bring to a simmer. Stir to combine. Reduce heat to medium and simmer until reduced and thickened, 7 to 10 minutes. Remove from heat; reserve 3 tablespoons for the basting sauce, leaving about 1/2 cup for the marinade.

Step 3

Transfer ½ cup banana ketchup to a bowl and add lemon-lime soda, soy sauce, garlic, brown sugar, black pepper, and lemon juice for the marinade. Whisk until combined. Add halved chicken thighs and toss to coat.

Step 4

Cover with plastic wrap and marinate in the refrigerator for 4 to 18 hours.

Step 5

When you are ready to cook the chicken, combine reserved 3 tablespoons banana ketchup, soy sauce, brown sugar, oil, and fish sauce in a small bowl for basting sauce.

Step 6

Preheat a charcoal grill until coals are very hot.

Step 7

Remove chicken from the refrigerator and place on metal skewers, folding in half with the smooth side on the outside, the rougher side folded in.

Step 8

Grill chicken over hot coals until no longer pink in the centers, 15 to 20 minutes, turning and basting every 2 to 3 minutes. Serve with accumulated juices or extra basting sauce.