I agree that 2 batteries won't be sufficient for a power hog. Anything that produces heat as its primary purpose, like a space heater or coffee maker needs a LOT of battery to supply it. If you can find a way to get 6 of the batteries in your bank, you will stand a better chance to get the coffee maker to work on an inverter.
When you find the watts of the coffee maker, divide by 10.9 to get the amps you need for the batteries to provide. That is 12v minus 10% for inefficiency in the battery/inverter system. E.G. a 1250 watt space heater would pull about 115 amps from the battery. That is huge. What size wire would you need to safely carry 115 amps? Is yours big enough?
Most folks make do with an old fashioned coffee pot on their propane stove top when not hooked up to a power pedestal.