In Japan, they're called "fujoshi" (腐女子) or "rotten girls", and they are into homoerotic "boys love" manga. The trend has spread to neighboring China, where "fujoshi" are called "funu" (腐女). Much of the appeal of boys love in both Japan and China is that the genre allows women to freely explore various roles—whether that is masculine males or effeminate characters.
And while boys love comics are classified as pornography in China, that does stop fans from creating their own fan fiction, comics, and here, energy drinks.
These cans of "big brother juice" are aimed at Chinese rotten girls and have been sold at funu fan events in the past. The can proclaims things like "One hundred percent natural big brother juice", "Does not contain little sister juice", and notes that the beverage is not intended for minors.
The drink is a parody of a well-known coconut energy drink, and it is not sold at regular convenience stores in China. So, yeah, milky white "big brother juice".
中国腐女子専用エナジードリンク『兄貴汁』が予想以上にウマイ / 缶には「防"腐"剤フリー」「動物性タンパク飲料かも？」など [ロケットニュース]