他们不吃早餐用英语可以说成 "They don't eat breakfast."
其中, "don't" 是 "do not" 的缩写形式，是英语中常用的否定形式。
下面是一些相关的英文例句及其中文翻译：
They don't eat breakfast. 他们不吃早餐。
I don't pke to eat breakfast early in the morning. 我不喜欢早上早吃早餐。
They don't usually have time for breakfast. 他们通常没时间吃早餐。
He doesn't eat breakfast because he is trying to lose weight. 他不吃早餐，因为他在试着减肥。