break a sweat
To put forth a large amount of energy or effort into or toward a task. Usually used in the negative to indicate the opposite. Likened to perspiring due to strenuous physical activity. That test was so easy, I aced it without even breaking a sweat. She didn't break a sweat becoming the district attorney.
break ˈsweat
(British English) (American English break a ˈsweat) (informal) use a lot of physical effort: He hardly needed to break sweat to reach the final.