Squeezing the bottle will do you absolutely NO good in keeping the bubbles in the pop. If it has any effect it all, it’s a negative effect: if the pressure inside the bottle is negative, due to the flexible bottle “trying” to regain its shape, that lessened pressure will cause more bubbles to escape. Only positive pressure will keep the bubbles in solution.
This is why pop in plastic bottles goes flat faster than that in glass bottles. Plastic bottles stretch, so if you agitate a plastic bottle half full of pop, the bubbles will escape. AT the point where a glass bottle’s rigidity does not allow the volume to expand any further, and the pressure equalizes, the plastic bottle will continue to stretch a little, thereby allowing more room for escaping gases. The glass bottle keeps the gas in solution because it doesn’t provide that extra escape volume. So when you open the bottle, there’s less gas to escape in a glass bottle, because it’s still in solution. Plastic bottle, the flex allows more escaped gas, which then escapes the bottle upon opening. Et viola, more escapes than with glass, so it goes flat sooner.