In a bowl, mix pineapple juice, whiskey, brown sugar, soy sauce, garlic, and fresh ginger until the sugar dissolves and the mixture looks glossy. The marinade should be evenly combined with no visible brown sugar clumps.

Set aside 1/3 cup of the marinade for basting. Cover and refrigerate it so you can use it during grilling.

Add the chicken thighs to the remaining marinade, ensuring they’re coated, then refrigerate for 1-4 hours. The longer the marinating time, the more pronounced the sweet-smoky whiskey-pineapple flavor becomes.

Preheat your grill to medium heat, then place the chicken on the grates. Grill for 6-7 minutes per side, basting frequently with the reserved marinade and watching for caramelized edges.

When the chicken is browned and cooked through, remove it from the grill and let it rest briefly while you finish the pineapple. Look for thick, glossy surfaces where the glaze has reduced and darkened.

Grill the pineapple slices over medium heat for 2 minutes per side. They should develop grill marks and turn slightly softened with lightly caramelized edges.

Serve the caramelized whiskey pineapple chicken topped or accompanied by the grilled pineapple slices. Spoon any extra glaze from the reserved marinade over the chicken for a glossy finish.