Cut 2 pounds boneless skinless chicken breast into 1 1/2 inch cubes. Place chicken breast pieces in a gallon-size resealable plastic bag. Pour in 1 cup grapefruit soda, 1/4 cup soy sauce, 1 tablespoon sesame oil, 1/4 cup brown sugar, 1 tablespoon prepared horseradish , 1 tablespoon minced garlic, and 1 tablespoon grated ginger. Gently massage the bag to combine all of the ingredients and make sure all of the chicken pieces are coated.
Refrigerate and let marinate at least 1 hour and up to 4 hours.
Soak wooden skewers in water for at least 30 minutes before use or use metal skewers.
Prepared the vegetables by slicing 1 medium zucchini into 1/4-inch coins, and cut 1 medium red bell pepper, 1 medium green bell pepper, and 1 medium red onion into 1-inch chunks. Transfer to a large mixing bowl and toss with 1 tablespoon vegetable oil, 1/2 teaspoon garlic powder, and 1/2 teaspoon onion powder to coat.
Preheat a grill to high heat (500℉). Remove the chicken from the fridge and thread onto skewers, alternating with pieces of the vegetables as desired.
Grill your chicken on a well-oiled grate, about ten minutes, until the chicken is cooked to an internal temperature of 165 degrees F, rotating every few minutes so that all sides receive grill marks. Serve hot.