Mix Pineapple juice, rice vinegar, minced garlic, red pepper paste, salt and pepper together in a medium bowl.
Trim and cube chicken breast and place into a bowl. Pour about ½ the marinade over the chicken and allow to sit for 30 minutes.
Cut the Peppers and Onions into chunks
In a large saute pan add 1-2 Tablespoons of olive oil and heat on medium. When hot, add chicken coated with marinade. Cook on medium for about 5 minutes or until chicken is no longer pink. Remove from pan and drain using a colander.
Return Chicken back to saute pan and turn on medium low. Add ⅛ cup of sugar to chicken and toss to coat.
continue to cook until chicken is browned and cooked through, about 5 minutes.
Place chicken in a clean bowl.
Heat saute pan over medium heat and add in chicken stock. Deglaze the pan and add in vegetables, remaining ¼ teaspoon of salt, remaining ⅛ cup sugar and remainder of the marinade. Cook over medium heat for 5 minutes or until vegetables just start to soften.
Combine 1 Tablespoon of cornstarch with 1-2 teaspoons of sauce from saute pan. Mix until smooth and pour into saute pan. Bring to boil for about 3 minutes. Repeat 1-2 more times until your sauce is the consistency you like.
Once the sauce is thick enough, turn heat to low and add pineapple chuncks and chicken, stir to combine. Cover and simmer on low for about 5 minutes or until warm. Serve over rice or lo mein noodles. Enjoy!