I stumbled upon this while looking up the usage of doch in "Hammer's German Grammar and Usage" (fourth ed), and the subsequent examples are from there. I am familiar with the use of doch for affirmative answers:
Bist du nicht zufrieden? -Doch!
Aren't you satisfied? -Yes, I am.
Kommt er bald? - Doch!
Is he coming soon? - Oh, yes
But the book also gives the following example:
Mutti, kann ich ein Stück Schokolade haben? --Nein doch, du hast jetzt genug gegessen.
Mummy, can I have a piece of chocolate? -Certainly not, you've had enough to eat
And the explanation accompanying it "When used with nein or nicht, doch emphasises a negative reply."
However, when I tried to make up example sentences to myself and ask native speakers about this usage, it did not sound idiomatic to them. Especially after considering the punctuation.
Does anyone have any further information on this? As a related question, how would one express the same sentiment (as the one meant by nein doch)? Perhaps by intensifying nein? Or something like keine Chance or Absolut nicht! ?
EDIT: added the translations provided in the book, in response to the comments about the second sentence.
EDIT The examples referenced above:
A: Kann ich dein T-Shirt leihen?
B: Nein doch. Das letzte Mal hast du Kaffee über meinen Pulli verschüttet.
A: Das Hemd ist ziemlich teuer.
B: Nicht doch. Es ist Seidenhemd und kostet nur 50 Euro.