Step 1: Get a clean new spray bottle!
You can find it as cheap as a dollar at the dollar store. Even if its new rinse it out befor using.

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I used to work at a company, where they had a refrigerator to keep your
lunch in. I liked to drink apple juice, and everytime I went to get some. It was dranken by some one else...
So, I got a glass bottle and made a Urine Sample label, and low and behold, no one ever drank any!!!
But you probably wanted to say LO and behold.
stil.... nice prank
You need to actually do this and take photographs of it.
L
When I'm refering to "Best!" and "Ever!", I'm speaking of the prank itself, not the actual instructable.
As for documenting it in photos, I have done the prank in the past, and did not have all the items on hand to do it, when I was writing the instructable. I wanted to enter in the prank in the contest so I used generic pictures. The instructions are super easy and don't really need visuals.
Now in regards to "Best!" and "Ever!". "Best" beacause of its ease to do and overall effect of the prank. "Ever" because window cleaner hasn't changed in a long time and is still toxic. It plays to classic notions that are still around today and will probably be around in the future as well.