The shaking of the container is adding energy to the environment. Also the shaking makes it easier for the liquid to be more evenly distributed within the container and therefore become a gas.

How much of a change in pressure also depends on the contents and the amount of shaking. Quickly shake a soda bottle can make it explode when you open it. Vigorously shake a bottle of water for an hour, almost nothing happens.

The lighter you mentioned, I don't think it would be unreasonable that it would reach a more gaseous state for a little while after you shake it. With the liquid more distributed by the shaking, it would definitely make it easier for it to become a gas when you open the lighter rather than its normal state of being pooled at the bottom of the container.