The workers were stuck in that poorly ventilated shed in the hot summer, which felt like a sweatbox.

sweatbox 是复合名词，由 sweat（汗水）和 box（箱子）组成。sweat 指"出汗"，box 指"封闭的空间"。 sweatbox 字面意思是"让人出汗的封闭空间"，用来比喻"闷热难耐的场所"，类似于中文的"蒸笼"。