Superficial friends; fair-weather friends; acquaintances who are friendly on the surface but lack true sincerity or loyalty.
小李发现那些平时称兄道弟的人，在他遇到困难时都成了面朋口友，没有一个伸出援手。
Xiao Li found that those who usually called him brothers all turned out to be superficial friends when he encountered difficulties; none of them offered a helping hand.
Next Idiom