Why don't you+动词原形。例句：Why don't you have a cup of hot water？为什么不喝一杯热水？
例句
1、Why don't you get yourself a car?
你为什么不买辆汽车呢？
2、Why don't you look in on me next time you're in town?
你下次进城顺便来看看我好吗？
3、Why don't you come over to England in the summer?
你为何不在夏天来英格兰呢？
4、You look hot ─ why don't you peel off?
你看来很热——为何不脱掉衣服？
5、It's very late now ─ why don't you sleep over?
现在已经很晚了——为什么不就睡这儿呢？