I will help you. Not!

[Sped Tiger]

I know that in English, it's grammatically incorrect to make a sentence without a subject and a verb, but what to do in such a case as the following onene part of the sentence is affirmative and the incomplete part is exclamative? How to make the sentence grammatically correct?
a. I will help you. Not! (part of conversation where someone's been asking someone else to help them, but the person doesn't want to help; their final answer)

 

[SoothingDave]

That is what we call an "interjection" and then we go on with our lives. No, it's not a grammatical sentence. It's just an utterance.

Like saying "wow!" when you see something spectacular.

 

[jutfrank]

I don't understand the question. Are you asking whether it's one sentence or two? Or are you asking how to write it properly? Why do think there's a missing subject and verb?

I can't even understand what the speaker is trying to do here. Do you mean something like this:

I will help you ... not!

 

[Barque]

@jutfrank This is common practice nowadays - people make a statement and then add "Not" to mean they don't agree with it.

Do you mean something like this:

I will help you ... not!

Yes.

 

[Glizdka]

Borat is known to be an expert at using not jokes.

 

[jutfrank]

For me it will always be associated with Wayne's World.

 

[Rover_KE]

A similar non-standard creative misuse of punctuation has become common recently when, for instance, a person has a horrendous day, is mugged and robbed, his wife is unfaithful, his dog dies, he gets the sack and moans to his mum - "Worst. Birthday. Ever".