The evaporator airflow can get blocked with frost or ice, causing the inside of the fridge or freezer to feel warm.
Where does the frost come from?
When you opened the refrigerator door to put the can of soda inside, Some of the ambient air enters the refrigerator.
That ambient air almost always has a lot of humidity in it, which is just water vapor suspended in the ambient air.
When that humidity hits the evaporator, running at about 14 degrees, it freezes immediately, forming frost. The more you open the refrigerator door, the more moist air you let in, and the more the frost will build up, eventually blocking airflow through the evaporator.
So What Do We Do About Frost?
Frost is simply ice; it can be melted. So right underneath the evaporator is a defrost heater.
Every few hours, a defrost timer shuts off the compressor and fans, and turns the heater on to melt the ice.
A drain pan beneath the evaporator drains the water to outside of the freezer compartment, where it evaporates back into the ambient air.
If the defrost heater or timer stops working, or the defrost drain gets clogged, ice can block the airflow, and it can cause the refrigerator to stop working correctly.