Coffein simply blocks the receptors in your body that send the signals to your brain that you are tired, while sugar is essentially pure energy. I’m no expert on this subject, but afaik both coffein and sugar increases blood pressure, which is probably not an ideal thing.
I have nothing but Amnesia: A Machine for Pigs to judge them on and based on that, they are very good at writing mysteries and cryptic stuff but they seem to be lighter on the gameplay side. From that, the writing will be good but hopefully it will have any gameplay.