The pineapple juice will give you an insulin spike, wich is good when you take gh..forces the hgh in your cells
insulin is a transport vehicle. spiking it or supplying the body with exogenous insulin multiplies the rate of metabolism (in this case protein synthesis).
think of slin as dump trucks delivering dirt (protein, sugar, nutrients, etc...) to the job site (your post-workout muscles). the more dump trucks the faster you're gonna get the job done.
so it pushes the raw materials into the cells--not the gh, but he's not that far off.
insulin, gh, and aas all work via different mechanisms to get you big.