That unit MIGHT charge an iPhone but it will never run a coffeemaker.
Most coffee makers draw 1200 to 1800 watts (not 100).
FYI - a 100 watt inverter will draw 8.33 amps (100 watts/12 volts) from your battery. A 1000 watt inverter will need 83.33 amps of battery supply. A 2000 watt inverter will need 166.67 amps of battery power.
An OEM battery has about 70AH of delivery that RAPIDLY decreases in capacity as the demand on each individual battery increases (see graph of a 100AH battery - you can use it for other batteries by making the capacity reduction a "percent").
So trying to get 83.3 amps out of a 100 AH battery will reduce the capacity to deliver TO about 5% of the rating.
A single fully charged OEM battery will not make a cup of coffee in an electric coffee maker (1500 watts or 125 amps). A PAIR will be hard pressed. (the demand on a single battery in a matched pair will be 1/2 of the load - or 62.5 amps).
Using the graph and a 100 AH battery, the supply will drop to about 25% of rated capacity (extrapolated and it could be worse!) with TWO batteries.
So two fully charged 70 AH batteries (140 AH total capacity reduced to 35 AH) will "make coffee" with an "average 1500 watt coffee maker drawing 125 amps) for about 35AH/125 amps or 0.28 hours (about 16 minutes or so before they are both dead).
If they are already reduced before you try to make coffee, they may not even deliver enough voltage at that reduced capacity to get above the low voltage cut out of your inverter.
If you intend to do crazy stuff like make coffee, use the microwave, or air conditioner, you will need to think about adding 500 pounds or so of battery bank 4 to 6 high capacity batteries.