Whisk the sugar, gluten free soy sauce, ketchup, white wine vinegar, sweet chili sauce, honey, red pepper flakes, ginger, garlic and pineapple juice together in a small bowl, set aside.
Place the whisked egg in a shallow dish.
In another shallow dish, add the corn starch and brown sugar and stir to combine.
Coat the cubes of chicken in the whisked egg, then lightly coat them in the corn starch mixture.
Set the battered chicken aside on a clean cutting board.
Heat the olive oil in a large skillet on the stove over medium high heat.
Once the oil is hot, add the battered chicken pieces.
Cook the chicken for 4-5 minutes, or until all sides are lightly browned.
Remove the chicken from the skillet and set aside.
Add the onions and diced bell peppers to the skillet, saute for 3-4 minutes.
Add the chicken back to the skillet, along with the pineapple chunks.
Pour the prepared sweet and sour sauce over the chicken.
Toss to cover the chicken and vegetables in sauce.
Cover and reduce heat to a simmer, cook for 10 minutes.