Heat a wok over medium-high heat until hot, add enough oil to coat the pan. When the oil is hot, add the chicken and saute for 3 -4 minutes.
Push the chicken to the side of the wok and add the onions and saute for 3 minutes.
Add the pepper and continue cooking for another 3 minutes. If you need a little more oil, add some.
Add the prepared sauce to the pan and stir to combine.
Add the pineapple chunks and stir again to combine. Let this cook for a couple of minutes.
Taste and season with salt and pepper. If you want to spice it up, add a little hot pepper flakes but this optional.