I have flavored coffee with zero calorie syrup, no creamer until its time to eat. Zero calories never breaks a fast.
Honestly, the syrup makes me like the coffee lots even without the cream! With OMAD I can have a real snack but I usually break it in half since one piece of cake is often 600 calories. My meal is about 1000 calories so I can fit that in on the holidays and still eat plenty healthy food too. And I do! And I do not gain weight doing this. I have to be very good until my daughter's wedding in August. Kids keep those wedding photos forever!