Are you certain all of the cargo holds are pressurized? I know that there is always at least one (also with temperature control) to help with the transport of animals. But thought that there were other sections not pressurized.
Wikipedia even explains “all modern commercial jets now have blow-out panels between pressurised compartments of the ‘plane, such as between the passenger and cargo spaces, to equalise destructive internal pressure differentials.”
Also, a plastic bottle is not gonna be anywhere near as robust as metal spray paint cans.