One of the popular Taiwanese drink that you'll find street vendors selling is Papaya Milk. It is kind of like a tropical papaya Smoothie or Shake. One of my early childhood memories is of my parent took me to a street vendor (in Taiwan) and buying me for my first cup of Papaya Milk.
In Taiwan, there is two kind of papaya milk. One is a cane of papaya milk and another one is fresh papaya milk. The best options and best taste would be the fresh papaya milk. Must get a try :)