If you had counterfeit fifty dollar bills, what would you buy? A basketful of groceries? Some new clothes? All the Taco Bell you can eat?
Or maybe you're worried that a big business will recognize your fake money, so you look for an unsuspecting rube to exchange your counterfeit $50 for smaller, real bills. Maybe that little girl running a lemonade stand to raise money for Alzheimer's research. If that's what you're thinking, congratulations -- you are a terrible person.