What must you do to apply a discount for a customer with a rewards card?

To apply a discount for a customer with a rewards card, scanning or inputting the rewards card is essential because the Starbucks register system is designed to recognize eligible rewards and discounts associated with that card. When the card is scanned, the system automatically retrieves the customer's account information, which includes any rewards or promotions available at that time. This process is streamlined for efficiency and ensures that the correct discount is applied without the need for additional manual input.

In contrast, asking for an email address does not directly relate to applying discounts but may be necessary for other account-related matters. Manually entering a discount code could lead to errors and is not the standard process for rewards card holders. Providing a paper coupon is also unnecessary as discounts for rewards card holders are typically processed digitally through the card itself. Thus, scanning or inputting the rewards card is the most effective and reliable way to apply the applicable discounts automatically.