Season chicken breasts with salt, pepper, and garlic powder.
Heat olive oil in a large skillet over medium heat. Add chicken and cook 5–6 minutes per side until golden and cooked through. Remove chicken and set aside.
In the same skillet, add pineapple tidbits with 1/4 cup of juice, brown sugar, soy sauce, and apple cider vinegar. Stir and bring to a simmer.
In a small bowl, whisk cornstarch with water. Stir slurry into skillet and simmer 1–2 minutes until sauce thickens slightly.
Return chicken to skillet and spoon sauce over chicken. Let simmer 2–3 minutes so chicken absorbs flavor.
Garnish with green onions and sesame seeds before serving.