what happens in the space above the soft drink in a closed bottle or can as the soft drink warms to room temperature

As the refrigerant begins to warm up to room temperature, the air inside the bottle that is between the refrigerant and the bottle cap begins to slowly come down. As you might already imagine, air in contact with the liquid can generate bubbles, and this is what happens when the air in the bottle starts to drop as the soda heats up.

Explanation:

You have seen that at room temperature it is common for soda to overflow bubbles. This is because the air inside the soda bottle begins to come down and when it comes in contact with the liquid causes a lot of bubbles and can even make the soda overflow.

When a soft drink starts to warm to room temperature, the air at the top of the can or bottle starts to sink into the water creating more bubbles and/or fizz. The space at the top of the can or bottle starts to shrink up.