preheat oven to 350 and prepare a 9x13 inch pan by lining it with foil and then spraying it with cooking spray.
in a large mixing bowl, combine cake mix, butter, egg, vanilla and mix.
the batter will be extremely thick and will be difficult to combine, but keep stirring or use your finger tips and knead it together, adding the water if necessary.
press the dough into the prepared pan. sprinkle the coconut evenly over the dough, then sprinkle whatever chips you may use evenly.
in mixing bowl (the same one from the cake mix is fine), combine the sweetened condensed milk and peanut butter, stir until well combined and pour mixture evenly over dough, using a spatula to even it out if necessary.
bake for 26-29 minutes, or until edges of bars begin to brown and pull away slightly from the sides of the pan, or until the middle of the bars has barely set, taking care not to over bake.
the bars will set up considerably upon cooling. allow the bars to cool well before slicing and serving. store in airtight container for up to 5 days or freeze for up to 3 months.