Generally, people think of the in-room units more as electric coolers than full-fledged refrigerators. The units do keep things cold although they may take a bit longer to cool down items. We always take a 6 pack of Coca-Cola with us to keep in our room and it's cold by the first evening.
As far as space, a pitcher would fit inside of the unit easily. Just guessing, I'd say the units are, maybe, 2 ft tall by 1.5 ft wide by 1 foot deep.