Heat a saucepan over medium heat. Combine the soy sauce, pineapple juice, sesame oil, honey, garlic, and red pepper flakes. Simmer until thick, about 5 minutes. Set aside to cool.
For at least 30 minutes, soak wooden skewers in water (if using) and soak chicken in half of the sauce. Reserve the other half.
Toss the vegetables in olive oil. Thread chicken, pineapple, and vegetables on skewers.
Broil for 5 minutes. Flip, drizzle the reserved sauce, and continue broiling for 5 minutes or until the chicken is cooked through.