Harry and Tom were sick. They were so sick, in fact, that they could not sleep for they were coughing and sneezing and just generally being sick all night. So, to solve this little issue, Harry took the Knight Bus out to Muggle London and bought himself a little miracle that Dudley had often been given when he fell ill; Nyquil.
Upon his return, Harry took a dose of Nyquil, hid it from Tom while smirking to himself, and slept peacefully for the first time in what felt like ages.
Tom, of course, was not happy with this development, as it meant that there would be no more sick-and-can't-fall-to-sleep midnight sex. This was not acceptable.
When Harry prepared to take his Nyquil the next night, Tom ran through the room and snatched the cursed Muggle product from his lover's hands before proceeding to dump it all down the toilet and flushing.
Harry retaliated by throwing the cap and measuring cup at the smug Dark Lord before leaving to take the Knight Bus back out to Muggle London to get some more miracle drugage.
Tom, who knew how to both Apparate and read minds, beat Harry to the store and, once Harry got there, picked him up bodily and Apparated them both home where he then proceeded to tie Harry up so he wouldn't escape again.
This, of course, presented a problem. How could they have sick-and-can't-fall-to-sleep midnight sex if Harry was tied down?
"Why don't you just get the damn Nyquil and we can both take it and sleep tonight then have make-up sex in the morning?!" Harry complained when Tom explained the problem to him.
Tom looked amazed. Genius! Why hadn't he thought of that. The Dark Lord frowned at his tied bed mate for a long moment before deciding that the lack of sleep was making it hard for him to think straight and leaving to get Harry's miracle Muggle product.
Upon Tom's return, he took the Nyquil, then left it just out of Harry's reach on the floor before going to bed.
With a call to his good friend Dobby, Harry was set free and got himself some Nyquil before kicking the peacefully slumbering Tom on to the floor and magicing the bottle of Nyquil to hang in the air above the Dark Lord's head.
When Tom woke the next morning, he enjoyed the feeling of a wonderful night's rest for all of five seconds before Harry's retaliation prank went off and dumped all over his face, making him sputter incoherently.
Harry poked his head over the edge of the bed with an evil smirk. "And there will be no sex for you this morning, Mr Riddle. You smell like medicine, and I don't allow people who smell like medicine to bugger me." Then Harry stuck out his tongue before skipping off to the bathroom.
Tom continued sputtering.