First, have a passion for what Jamba Juice does. They make healthy smoothies for customers. As we have stated throughout this answer guide, it is very important to have the same passion for healthy meal options as Jamba Juice does, and to take your own healthy eating seriously. With that said, you can easily tell the interviewer about your own experiences and how they are aligned with Jamba Juice as a reason you want to work for the company.
Second, think about your own situation. Are you currently in High School? Great, tell them you would love the opportunity to work at Jamba Juice, because you love the company, and want to start saving money for college and would really appreciate this job. Are you in college? Simple; say you are a frequent visitor of Jamba Juice, and would love to work here so you can afford basic college expenses, such as books and your meal plan.
Remember, try to align your passion with Jamba Juice first, before talking about money. No interviewer wants to hear your only reason for working at ANY company is simply for the money.