Well being that coffee is a zero calorie drink (unless you take it with cream and sugar) I don't see why having your regular amount of coffee should get in the way of doing OMAD. I personally wouldn't be able to do four cups of coffee, especially two on an empty stomach, but that's because I have a caffeine sensitivity.
As long as you're drinking your coffee black, without sugar, I think there should be zero issues. Drinking coffee while dieting actually might have some benefits, as coffee is known to temporarily increase your metabolic rate and suppress appetite.