Sweet, milky and colorful — bubble tea is wildly popular in China, where people sipping through straws from large plastic cups is a common sight in high streets and shopping malls across the country.

But there's fresh competition brewing in the vast market, characterized by ultra-cheap products that are striking a chord with China's increasingly frugal young consumers.

Bubble tea — which classically includes tapioca balls and comes in a wide range of flavors, with or without milk — has gained huge popularity in China, coinciding with an economic boom in recent decades that propelled living standards upwards.