for doing VS to do something

[QingqingW554]

Hi dear instructors,
Could I ask two sentences that come from the Manhattan Grammar BOOK 6th.

Right: She drank coffee to stay awake.
She drank coffee in order to stay awake.
Wrong: She drank coffee FOR STAYING awake.

I don't understand why "for staying " is wrong in this sentence.
I have seen this explanation in the Longman Dictionary:

" used to say what the purpose of an object, action etc is
for doing something:
a knife for cutting bread
What did you do that for?
I’ve bought him a watch for his birthday.
the documents prepared for his defence"

then, My question is why we could not use "For Staying awake" to express the purpose of drinking coffee is to stay awake ?

Thanks in advance !

Regards
Claire

[Sage Pearce-Higgins]

Good question. I agree that our guide is a bit misleading here, as the construction "for -ing" clearly can be right in some situations. Your example of 'a knife for cutting bread' is a totally fine. And obviously "for" has many other correct uses too.

There is, however, a distinction between a process / repeated activity and a result which throws up some wrong sentences. Use your ear to decide if the following examples are correct, and then analyze why:

Can I borrow your bicycle for getting to class on time?
He keeps a gun for shooting animals.
He pulled out his gun for shooting the intruder.
This is a machine to make coffee.