"Sugar Free" / "Sugar, Free"

I just submitted the following funny true story to Reader's Digest:

When I came to the United States in the 80's as a refugee from a war-torn country, I craved sweet things and did not have a lot of money. One day in the school's cafeteria, I noticed a small placard in front of cupcakes with these two magic words: "sugar" and "free". I grabbed a couple. The cashier charged me for both.