“I could do with a coffee.”就是“我真想来杯咖啡”

“I could do with a coffee.”不是“我能处理一杯咖啡”，而是“我现在真想来一杯咖啡”。could do with表示需要某物或有了它会受益，语气通常比I need更随和。

例如走完一段长路后可说：“I could do with a coffee. How about you?” 这也可以只是轻松提议。really会加强语气：“I could really do with a break.”美式英语更常说I could use a coffee。

https://dictionary.cambridge.org/dictionary/english/could-do-with
https://www.collinsdictionary.com/dictionary/english/could-do-with