I think this more of those “It depends” situations. Does the caffeinated drink have sugar? How many crackers? Which biological processes are you using to get a benefit from?

If there’s no sugar in coffee, you’re body stays in a fasting state*. If you eat three crackers, you might not cause the body to release insulin. But if you’re looking to get the benefits from ketosis, then those crackers will be a problem.

So, it depends. But zero is the safest answer.

* The article says it may interrupt autophagy