Capping a Container While Applying Pressure to Contents

What is the current sate of the art in capping containers with internal pressure? Not spray-paint cans, but for instance, if I wanted to pressurize plastic antifreeze bottles to prevent collapse when stacking the pallets in a hot warehouse? Heavier(thicker) bottles are cost prohibitive, so we are looking at nitrogen injection in the fill process.

Should we try to saturate the liquid with gas (as in a carbonated beverage) before filling, or at some point during the capping process?

Any foreseeable problems with chemical reactions or interactions between the gas and the liquid?

Any suggestions, or other ideas?

Thanks in advance for taking the time to consider my problem and render your excellent advice.