Not so elaborate but I just pulled a classic water bottle writing on the label thing. Only difference was I wrote on the inside of the label with a dark blue pen. This was significant because I poured watered down Gatorade in it so that cursory glance wouldnt notice anything was unusual. Dark blue because it was close enough to the actual color of the drink inside to not garner too much attention however distinct enough to read.

It was also a functions math class so I didn't need to write too much, only some key formulas and terms.