John had accepted long ago that Sherlock absolutely did not sleep while on a case.
"Sleep slows me down, taking up ample time that I could be using to solve the case," Sherlock would say. "Sleep is boring."
Unfortunately, John knew otherwise.
No matter how much Sherlock denied the necessity of sleep, John could tell that as the days would go on he would gradually become more and more irritable and less and less attentive. The people at Scotland Yard, in their mutual distaste and ignorance towards him, just chalked it up to Sherlock being Sherlock as he advanced towards solved the case. But, John, being the medical man, would instantly know it as sleep deprivation.
However, regular subtle begging on John's part would do little to convince the great Sherlock Holmes to retire to bed for even as so much as a catnap.
"Sleep is boring."
And so John would do as he always did when he couldn't get his way with his friend's health: sigh and go to the kitchen to make tea.
But this is where it all changes up.
John would return from the kitchen with a single hot mug of chamomile tea, place it at Sherlock's side and then go upstairs to his room to update his blog. After about a half an hour, John would return downstairs under the excuse of doing some menial task while in actuality he was checking to see if his secret weapon had worked.
No matter where John had left Sherlock before the tea (sulking on the couch, yelling at the telly from the armchair, fiddling with experiments at the dinner table), the result was always the same: the tea half-drunk and Sherlock sprawled about fast asleep. Generally, at this point, John would just tuck a blanket around the unconscious body and go to bed himself, but, sometimes, if he felt up to it, John would also try to prod Sherlock to get to his own bed for a rest that would guarantee a steady night's sleep.
"Sherlock," John would whisper, shaking him.
"Hnnnn…" Sherlock would sigh sleepily.
"Sherlock, go to bed."
"No, Johnnnnn…"
"Sherlock."
"Iamm not tirrreeed…"
"C'mon, Sherlock, I'll get you to bed."
And so John would carefully hoist Sherlock up and guide him, half-asleep and mumbling incoherently the whole way through, to his bedroom and lay him down.
"Now that wasn't so bad, was it?" John would chuckle as he leaned on Sherlock's bedpost. There was never a response from the detective at this point, because he was usually out as soon as his head hit the pillow.
And so John would sigh contently, because he didn't mind. It rather reminded him of taking care of his sister, Harry.
In the morning, whether he had woken up in bed or elsewhere, Sherlock would complain loudly about having fallen asleep and how much it had set him back and oh by the way the brother is the murderer so text Lestrade as soon as you can and-
John would just smile and drink his morning cup of tea, because Sherlock never would question how he ended up asleep on the couch or in his bed, and John never would tell him.
And that was perfectly fine for the both of them.