You must study how the QR coding works. Then you can modify the codes. It's probably easier to create your own, print them out the right size on labels, and stick them over the original codes. Perhaps link to this site, or perhaps Rick-roll people. That's always a lot of fun.
I tested this idea. QR code seems to have a lot of redundant squares. I couldn't make it fail.
You must study how the QR coding works. Then you can modify the codes. It's probably easier to create your own, print them out the right size on labels, and stick them over the original codes. Perhaps link to this site, or perhaps Rick-roll people. That's always a lot of fun.
Spray paint would do it
The point is to use a sharpie because you can control it very easily and at a glance no one would know.