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. “Everything that Chief secretes in a normal day goes into the suit and is recycled through capillary action powered by the Spartan’s body movement,” he said. “Catheter implies invasion but really is used in the Mjolnir sense to describe a hygienic valve system. Thank goodness for 26th-century supermaterials and bespoke tailoring. Capillary action happens after the voiding. Recycling is almost perfectly efficient,” concluded O’Connor.
As for sleeping… Well… He closes his eyes.
it isnt easy to get out or in of the suit , so the suit does most of the funtions of hygenic nature . eating of course he simply takes of helmet but i guess there is also somekind of tube inside the helmet , or injection when he needs to eat maybe in contaminated envirmorent , similar to how gasmasks have a drinking valve . technically speaking he probably dosent have to take off the armor. there was a text passage in halo the flood where he was taking the armor of for a shower , but i think it was retconed since.