It means to be jealous.
Here’s a story about 吃醋（chī cù）.
The wife of a Tang dynasty prime minister Fang Xuanling was jealous because the emperor Li Shimin wanted to give Fang Xuanling several concubines.
But Fang Xuanling dared not accept them.
The emperor said to Fang Xuanling’s wife, “if you don’t accept your husband to have concubines, then you drink this poisoned wine.”
His wife took the poisoned wine and drank it immediately.
In fact, the emperor gave her only a pot of vinegar, it is just a test.
Hence”吃醋（drink vinegar）means “jealous”.