How does Master Chief do normal everyday functions such as eat, drink, toilet and sleep? To eat and drink he takes his helmet off. For bathroom breaks, this is what Frank said on the subject: Frank O'Connor, creative director at Microsoft, also touched on the subject.

Does the Master Chief ever sleep?

He was augmented as a child, he has spent many years in cryo-sleep, and the Librarian did the evolution thing to him in Halo 4. For all we know, the Chief is now immortal.

Do Spartans in Halo eat?

They eat by removing their helmets and eating the food.