Question

Is there anything I can do for you?

Answer 1

Is there anything I can do for you?

我能帮你做些什么吗?

选No,thank you just the same

不用了,还是得谢谢你.

I feel it is unnecessary 我觉得没必要（不礼貌的回答）

It's impossible 那是不可能的（不礼貌的回答）

There's no need没有必要（不礼貌的回答）