John chomps and chews away, humming to himself while he works at the ties on his chair. He manages to free it from the mountain of cushions and sinks down into it with a sigh. The gum had lost its flavor a while ago, but he is enjoying irritating his flatmate. He picks up a pillow lying next to his foot and chucks it at Sherlock who hasn't moved for a half hour now.
"Hmmf."
'Fine, if you get to be an annoying sod, it's my turn, Sherlock.' John grips another small pillow and tosses it between his hands. He winds up his arm and throws it hard, aiming for the back of the sofa above Sherlock's head.
Whump.
The pillow bounces off and falls onto Sherlock's still form. John grins, but the novelty is slowly wearing off because Sherlock won't give a satisfying response. He gets up and heads into the kitchen to spit out the gum that was shredding and turning tacky.
Sherlock flips over and sits up, planting his feet on the floor. "Finally! You stopped that incessant chewing!"
John walks nonchalantly back to his chair and sits. He reaches down over the armrest and just barely grabs the pack of gum. He supresses a giggle, settling a smirk on his face.
John holds a steady eye contact with Sherlock while he unwraps another piece and pops it into his mouth, biting down.
...
Sherlock glares at him and reaches under the sofa for his laptop. He draws his legs up and crosses them to place his laptop on them, ignoring the hard wooden frame of the sofa beneath him. He snaps it open and furiously types away.
Why chewing gum is bad for your health
Sherlock hits enter and scans over the brief summaries of the search results. 'I'll show him. John's a doctor, surely he knows the bad effects of gum; bloating, gas, excessive production of stomach acid, erosion of enamel, the irritation of EVERY PERSON AROUND HIM.'
Sherlock takes a deep breath, calms his thoughts, focusing them, and starts piecing together a presentation of the pros, and more importantly, the cons of chewing gum when his process is interrupted.
POP
Sherlock tears his eyes away from the screen to see John pulling the popped bubble off of his face and back into his mouth. Sherlock screws up his face and hopes his expression perfectly matches his thoughts. 'Disgusting.'
John simply hums and doesn't so much as glance over to where Sherlock is boring a hole into John's uninjured shoulder with his glare. John had picked up a book to read and was settled back comfortably in his seat.
Sherlock places his laptop to the side. Any presentation of facts would be ineffective considering John's determination to pester him. Sherlock props his elbows on his thighs and rests his chin above his steepled hands. He closes his eyes and hears the 'shhoo' of the bubble expanding this time and–
POP
Despite paying attention for the pop, it was much louder this time and Sherlock involuntarily jumps at the sound. His eyes fly open and he snatches up his laptop, marches over to grab his mobile from his desk, and continues right on into his room, slamming the door.
He flops onto his bed and lets out a muffled groan into his pillow. 'A case!' That's what the consulting detective needs. A case that needs his brilliant deductive talents. Sherlock turns on his mobile to send a text to Lestrade.
Case!–SH
Sherlock twiddles the device between his fingers as he waits for a response.
Nothing right now.–GL
Sherlock throws the mobile at a blanket he had tossed to the floor and swipes his palm down his face, breathing in. 'Mint?' He sniffs his fingers, the scent is faint, but distinct; Sherlock definitely smells mint. 'Must still be on my fingers.'
Had this been a cartoon, a lightbulb would have comically appeared above the dark curls on Sherlock's head and lit up. What actually happens is, Sherlock bounces to a sitting position and his eyes dance around, his mind formulating an experiment. He scrambles for his mobile to type out a number by memory and prepares another text.
'Need groceries.–SH'
His mobile buzzes moments later.
'Shopping list?'
Sherlock sends a few more texts before sitting back. 'Time to get rid of John for a bit.' After a few minutes, he hears his flatmate's mobile ring and some muffled conversation through the closed door before John shouts from the living room.
"Got called into surgery again, I'll be a while."
Sherlock doesn't answer and the door to the flat clicks shut. Sherlock leaves his room and watches John get in a taxi from the living room window.
Sherlock waits a few more minutes, then pulls his long coat over his pyjamas, slipping on his shoes. He treads down the stairs and walks out of the building to trade off some money for a plastic grocery bag with his supplies. He trudges back to the flat, taking a peek at the contents of the bag.
'Surely, this will at least occupy some time while I'm bored.'