Sure, but watch the caffeine. I’m not saying you need to go cold-turkey on caffeine in order to do Bright Line Eating, but keep in mind that caffeine is a drug, so it will release unnatural levels of dopamine into that pleasure/reward center you’re trying to let heal. Excessive caffeine intake is definitely not a good idea.
If you drink coffee or caffeinated tea, try committing to a specific quantity, like one cup in the morning, or perhaps one cup in the morning and one in the late morning. I would keep it to two cups max.
Decaffeinated coffee is better, as long as you drink it black. Remember, though, even decaffeinated coffee has some caffeine in it. Avoid drinking it after mid-day so it doesn’t disrupt your sleep. When you do Bright Line Eating, your system will get really clean and decaf will have a bigger impact on you than it used to. Also, be ever mindful of the hand-to-mouth crutch, and if you find you’re drinking decaf coffee in excess, you may want to let it go.
The other consideration is many of us are used to dumping sugar and cream into coffee. Sugar is obviously out, and so are artificial sweeteners, but milk or cream is also adding calories outside of a meal, so that’s out too. So if you can drink your coffee black, then by all means, go ahead.