Anyone else ever do this trick? Go to a restaurant. Wait until the waitress brings the check. Then as soon as she sits it down be like, "oh shucks, I wanted a cup of coffee". In my experience like literally 85%+ of the time she just gives it to you without trying to add it to your ticket. Coffee costs like 2 cents a cup to them anyways, so they do not consider it a big deal. Plus, if she tries to add it, you can just stop her and tell her its OK you've had enough caffeine already.
You are welcome OG.