Make the sauce by placing the ketchup, soy sauce, honey, mustard, brown sugar, lemon juice, and garlic into a small saucepan. Cook on medium-low for 20 minutes, stirring often.
Make the skewers by threading the chicken and pineapple pieces onto wooden skewers or kebab sticks, alternating them. Season with sea salt and freshly cracked pepper to taste.
Pour half of the sauce into a small bowl, reserving the rest for serving, then brush the skewers with the sauce.
Heat a large grill pan over medium-high heat and drizzle the pan with olive oil.
Cook the skewers for 2 minutes on each side (4 sides) for a total of 8 minutes, or until the chicken is cooked through.
Remove the finished skewers from the pan and place them on a serving tray.
Serve the skewers with the remaining half of the barbecue sauce. Enjoy.