The refrigerators in the staterooms are the "servi-bar" variety (that was their original intent), and somewhere between 2 and 3 cubic feet. As a refrigerator, they are not very efficient (they are quiet though). They'll keep cold things cold, but don't do too well to cool ambient items to fridge temperatures very quickly.
If you are interested in refrigerating soda, plan to cool first with ice then put them in the fridge and they'll hold.
I've read that some staterooms had better cooling capacity, pehaps by better or more recently maintained equipment?