Place the chicken breasts in a large gallon-size bag or a baking dish.
Mix up the marinade by combining soy sauce, ketchup, finely chopped pineapple, pineapple juice, honey, vinegar, and sriracha in a bowl. Pour half of the marinade over the chicken and reserve the rest for later. Refrigerate for at least 30 minutes or up to 2 hours.
When it’s grill time, take the chicken out of the fridge and let it sit for 10-15 minutes. Preheat your grill to 450ºF and clean the grill grate or lay down a piece of aluminum foil.
Season the pineapple slices with chili powder and salt.
Grill the marinated chicken over direct heat for about 8 minutes per side.
Grill the pineapple for 2-3 minutes per side until grill marks appear. Remove from the grill.
While the chicken cooks, pour the reserved marinade into a saucepan and bring to a boil. Let it simmer for 2-3 minutes, then remove from heat.
Once the chicken reaches an internal temperature of 165ºF, remove it from the grill.
Serve the grilled pineapple over the chicken and drizzle with the remaining marinade. Dig in and enjoy!