^it' an asian drink... with a "tea" base. You can get either milky tea or slushy. And it comes in basically any flavor you can (or wouldn't have thought of). And if you like you can add "pearls" which are either made up of coconut jelly or tapioca.
from bubbleteasupply.com: Bubble drinks are usually cool, refreshing, and a sweet drink with tapioca pearls sitting on the bottom of a clear cup. Sometimes the drink is made with fresh fruits, milk, and crushed ice to create a healthy milk shake. You can also find drinks that are made of powdered flavoring, creamer, water, and crushed ice. And if you like it like the Asians do, the cool drink usually includes a healthy tea, infused by a flavoring.