Er, no explanation? ...Enjoy...?
Sasuke's memory is bad.
Well, it's at least "selective." Because of some traumatizing incidents (the same ones that caused Sasuke to move to arid Suna and away from his home town) he subconsciously blocks out and forgets things quickly. Especially those with negative connotations for him, such as remembering a new showerhead for the bathroom since his drowning was attempted in a similar place, or those that carry the potential to be painful like getting more eggs because if any of them are cracked the whip will be the next thing cracked, boy.
Of course, Sasori is as understanding of this as he can be (he has his own faults, you know, which can also be fixed by therapy but which he uses medicine to fix instead).
This is what the sticky notes are for. They are a precious thing to Sasuke. They represent a doorway to normalcy, a way to force his memory into working when it tends to refuse. So it should be perfectly understandable when he gets pissed about Sasori diminishing the significance of them with random scribbling.
"Don't forget" reads the top one. The one underneath says, "Wish the neighbors would take down their Christmas lights wtf~~".Beneath that is the actual words "scribble scribble scribble" (god Sasori has sunk so low) and then "Dei said hi".
Sasuke bristles at these notes, throwing them in the trash one by one. The second to last one in the stack says, "milk eggs cake mix, strawberry if possible, Dei's favourite". Sasuke folds this one and puts in his pocket to take to the store with him.
He is going to throw the last one away without looking (after all, Sasori can probably only manage one relevant note per pile) but his eyes sweep over it without his consent.
"Had to reorganize the cupboard again. Hope you don't mind… sorry."
Sasuke regards the note with a bit of disdain. He sighs and pulls a pen out of his pocket. He writes "It's okay, don't stress," under Sasori's ultra-obsessively neat writing, and then "Just do the fridge next time, too" with a little smiley face next to it. And then he takes another sticky note and writes, "Thursday's therapy canceled. If on edge, please don't push" and sticks them both to the fridge.
He has to check the locks on all the doors before he leaves, just like he always does.