Heat a splash of olive oil in a large skillet or wok over medium heat.
Toss in the diced chicken, season with salt and pepper, and cook until browned and cooked through. Set aside.
In the same pan, add a bit more oil, then sauté garlic and red bell pepper until soft.
Scoot the veggies to the side, crack in the egg (if using), scramble it, and mix it all up.
Add the cold rice, breaking up clumps. Stir-fry for 2–3 minutes.
Return the chicken to the pan, throw in the pineapple chunks, soy sauce, sesame oil, and pineapple juice.
Cook for another 5 minutes, stirring often, until everything’s hot and the flavors have made friends.
Top with green onions and serve hot. Maybe with chopsticks, if you’re feeling fancy.