"Sherlock, what the bloody hell is in the sink?"
Sherlock shrugs dismissively, avoiding eye contact by focusing on the microscope in front of him. He says nothing, in the hopes that John will simply go away.
John, however, has other plans. He sits at the table across from Sherlock, waiting patiently. He'll have to look up eventually. Sighing dramatically, Sherlock gives up, turning the knob on the scope as he pulls away from the eyepiece.
"Can I help you with something?"
"Sherlock," John sounds defeated already, before even having made his point. "We've discussed this. Anything that was ever inside any human being doesn't go where food or dishes go. This includes the top three shelves of the fridge, the cupboards, and shockingly enough, the sink." He pinches the bridge of his nose before looking at Sherlock, who looks surprisingly chastened.
"I am trying. Contrary to what everyone has told you, I do have some concern for your comfort and wellbeing. I've just gotten so settled in these..." he waves his hand in the air, looking for a suitable word "bad habits, that it's difficult sometimes."
"Thank you, Sherlock. I don't say this enough, but I do appreciate your efforts." John smiles, getting up to make them both some toast.
"Erm, John, you might want to consider avoiding the bread bin..."