Good morning Jane. The reason it is correct to say, ´What about some coffee?´ is because a limited quantity is implied. You are offering or requesting a certain amount of coffee (for example, one cup. ) In addition, although any is normally used in questions, some is used when making offers or requests. I hope this helps. Kind regards, Nicci

да, это ж про "немножко", а не "хоть какое-то"