Despite what many have said, the "Beverage Coolers" are more similar to mini-refrigerators than coolers. They plug into an electrical outlet, have condensation coils, and fans in the rear.
Although they may not be full-fledged refrigerators, they do keep things cold. (As a comparison, even the plug-in thermoelectric coolers sold at shops like Wal mart or K-Mart can keep items 40 degrees cooler than the surrounding temp. If your room is kept at 75 degrees, then the drinks would be 35 degrees. Sounds cold to me.)
We always bring canned Coke onboard and have never had problems with it not being cold by the next day after placing it in the fridge.