Just got back from a week on the Voyager of the Seas. They have plenty of outlets to plug things in, so I wouldn't imagine bringing a coffee maker would be a problem. Just make sure to unplug/turn off before leaving.
And yeah- you can bring soda and water and put it in the fridge. They have that stuff in the fridge for you to buy too, so it's a matter of how many things you want to lug on board.