Anybody that thinks you can sell ice cream asking questions like this on the Internet needs to go back and revisit Marketing 101.
If you have an IQ greater than your age, you can look at ice cream and tell if it has been scooped or if it comes from a machine. But assuming you are unable to figure that out, the next step would be to watch what the employee does. Pay attention, it will happen immediately after he/she picks up the cup.