Coffee (black) is already low-carb. Now, what you choose to put in it, on the other hand...
I know. I'm a four shot espresso man topped off with enough hot water to make one cup or mug. I gave up drip/perked/pressed coffee a few years back. I use a stovetop espresso maker($12.00) and a hand plunger milk foamer($18.00). I use the foamer to make hot chocolate for me and the kids. Try it sometime. Best hot cocoa on the planet. Foams so thick you can mistake it for marshmallow.