Would you like a cup of tea?

你想要一杯茶吗？

There's no coffee - would you like a cup of tea instead?

没有咖啡了，你要不要来杯茶？

Would you like a cup of tea before you go?

走之前想喝杯茶吗？

Would you like a cup of tea?Yes, please. No, thanks.

你想要一杯茶吗？是的，想要。/不，谢谢。