Breakfast? Depends on the workout.
Coffee? I’m not going.
On a more serious note, I can usually make it through shorter anaerobic repeats or sprints fasted, but sweetspot/threshold intervals are significantly easier if I’ve eaten beforehand. I know some people are fine with fasted v02 work, but personally I struggle with that in the first place so I’d rather go in with the best possible chance of success 
Obviously there are some benefits to fasted endurance training, but I personally don’t find it beneficial to higher-intensity work- not only are you potentially limiting the amount of work you’re able to do, it’s also way more unpleasant IMO and makes it harder to complete workouts.