They're calling the promotion the "3pm Wake-Up Call" and it's valid on any size and flavor handcrafted Starbucks Refresher (i.e. it's not valid on the canned version), including the new Valencia Orange flavor.
The company sees the late afternoon as the ideal time for customers to get a quick caffeine pick-me-up and are positioning the Refreshers for that daypart.
Starbucks Refreshers comes in three flavors: the aforementioned new Valencia Orange plus Cool Lime and Very Hibiscus Berry.