Q. What can I substitute for cocoa powder if all I have in the house is Nestle's Quick?
That's a little like asking, "How do I get this egg back in the shell?" There's not really any way to substitute Nestlé's Nesquik (the name was changed in 1999) for cocoa powder, unless you're making chocolate milk or hot cocoa. The ingredients in the chocolate version of Nesquik are sugar, cocoa processed with alkali, soy lecithin, salt, artificial and natural flavors, and maltodextrin. How are you going to work those extra ingredients into your recipe? And how do you know how much sugar there is relative to the cocoa, so that you get the right amount of each in your recipe? And what are those artificial flavors going to do to your finished product?
We suppose it is not beyond the realm of possibility to substitute Nesquik for cocoa and sugar in some simple cake recipe, but unless a trip to the store is absolutely impossible, we'd put off the baking project until we purchased some plain cocoa.
Nesquik powder is available in several flavors: double chocolate, artificially sweetened chocolate, and strawberry, and the ready-to-drink versions of Nesquik are available in those flavors as well as banana and "very vanilla." We absolutely forbid you to try cooking with any of them!