In the end, John orders pizza. He manages to convince Sherlock to eat some too, and Sherlock is still too shocked at the reciprocation of his feelings to protest. Though Sherlock had intended to solve the case tonight, in the end the evening is spent on the sofa with John, stretched full-length, head in John's lap, ostensibly re-cataloguing his mind palace, really half-dozing with John carding fingers through his curls.
Neither speaks for the rest of the evening. There is no need for words, and no words that would suffice anyway. Instead they quietly stay there, John half-reading but in reality marvelling at getting to touch Sherlock like this, at getting to have him fall asleep across his legs - for it isn't long before he is asleep, breaths soft and even, hands falling away from their customary prayer position. And John - for his own part - doesn't have the heart to move, can't bear even the thought of disturbing Sherlock from this peace. So although he knows full well that his back will hate him in the morning, he allows himself to fall asleep too. (Oddly enough, though they never left the flat and hardly spoke a word, it's still been better than his first dates tend to go.)
It's Mrs Hudson who finds them, when she goes up in the morning with Sherlock's tea. Both are still asleep, though curled in on each other now so that it's difficult to tell where one ends and the other begins. She doesn't say a word, instead smiles knowingly and gets a blanket. (There's no use in letting the boys get cold, after all.)