Antonyms for the phrase "broke a sweat" would include expressions like "stayed cool," "kept calm," "remained relaxed," or "maintained composure." These phrases suggest a sense of ease, comfort or nonchalance. Another antonym could be "did not exert oneself," indicating a lack of effort or physical activity. Other phrases, such as "did not break a sweat," "did not perspire," or "did not work up a sweat," further suggest that the individual did not experience any physical distress or strain, and instead remained relaxed and at ease. In a literal sense, antonyms for this phrase could include "shivering with cold" or "sitting in a cool breeze.