work like a slave
To work very intensely for a long or continuous period of time, especially doing something thankless or menial. The boss had us working like slaves to get the project ready on time. I worked like a slave the entire summer after high school to earn enough cash to buy my first guitar. I've been out here working like a slave while you sit inside sipping lemonade. Could you maybe lend me a hand?
ˌwork like a ˈdog/ˈslave/ˈTrojan
(informal) work very hard: She worked like a slave to pass her exams. OPPOSITE: not do a stroke (of work)