A Tip and a Treat

I was at my local small to midsize city airport when I purchased a small cup of hot black coffee. I received a 16oz cup (their smallest size) with a thin sleeve for $4.22. Would I like to add a tip?

I then purchased two granola bars and the total neared $10 (my brain resisted retaining the exact total, a natural trauma response). Would I like to add a special treat for the troops?

As I thought it unlikely for the troops to invade the airport and bring with them stacks of 12oz coffee cups with thick sleeves and 20% discounts, I declined. Politely, of course.