字面上可改为：Don't come in or have any water.相当于：Don't come in and don't have any water.
但实际上是没有这种情况的.这本是口语中的一句邀请话,意为：请进来喝杯茶.是先进来然后喝茶,后者是承前者发生的,既然不进来,也就无所谓喝茶了.即,没了前者也就没有后者.
我个人认为,既然Come in and have some water.与Will you come in and have some water?相当, 只不过后者比前者更委婉些,那么前者的否定就可用 Won't you come in and have some water?来构成否定.
以上为一家之言,仅供参考.