Starbucks really wants you to make small talk with customers like asking about their day. They also want you to remember regulars, their names and their drink orders. It's all about the "customer connection". For example, when I was asked this question I talked about a customer who would come into my work frequently who was a college student. I would ask him about his classes and tests, etc.

If asked this question, you could just say "I have no prior work experience so I can't personally speak to this, but hypothetically this is what I would say/do"