When you do so much homework without any break that your brain gets hungover and you can't think about shit. This leads to getting some delicious snack that's for "Thinking purposes"
Bob: I'm hungover, I need a brain snack.
Bill: Bitch, you're just finding another excuse to eat something you fat slob.
When you constantly work and your brain is so hungover you need to take a break and have a "Brain Snack".
Bob: Damn, so much work, I need a brain snack
Bob (Sub conscious): Stop eating you fat slob