How about having some coffee? 要不要喝點咖啡？這句文法結構如何講,主詞?動詞?

How about having some coffee?
這是在「做建議」，可能得到yes/no的回應。也可以說成：What about having some coffee?
how/what是疑問詞＋about介系詞＋having some coffee動名詞片語
動名詞片語是介系詞about的受詞
因為其中沒有「主詞」或「動詞」。在文法上，全部應視為一個「獨立使用的片語」（本身有完整的語意）。
What about having some coffee? = Do you want to have some coffee?
前者說法比後者簡潔。

How about xxx/what about xxx 也可以用來「詢問」資訊：
I'll post your letters.  But what about (how about) this parcel?

How about your parents?  Are they well?

How about "you"
How "do you think" about "you all" 
=Have "you" had---------subject+vt;
active voice;
"Have" meaning drink
some coffee------------reflexive verb with cognate object follows same related verb "Have-had"in the pattern.