In a gallon-sized sealable plastic bag, combine pineapple juice, honey, brown sugar, soy sauce, ketchup, mustard, garlic, and onion powder. Knead bag until well-combined.

Add chicken tenderloins to marinade and knead bag to coat evenly.

Place in fridge 1-6 hours to marinade.

Heat griddle to medium-high heat and coat the surface with a thin layer of olive oil.

Place chicken on griddle and cook for approximately 8-10 minutes (until internal temperature reaches 165 degrees), turning chicken every two minutes.

(Optional) Add fresh pineapple to a different part of griddle and cook for 5 minutes, turning occasionally. Serve pineapple with chicken.