Similar to the Cadbury chocolate bar hack => http://www.ozbargain.com.au/node/32316
7/11 has another "Rip & Win" promotion going on with the top prize being an iPad, as well as small consolation prizes like Super Slurpees and other things.
Conveniently, the sticker is somewhat see-through. You could easily see "Free Super Slurpee" on the cup that I (well, the boyfriend) picked up today in about two seconds.
So grab a few LARGE cups and have a look for "Free Super Slurpee", and if you win an iPad, well.. I'll take it. Kidding. :P
Oh, and unlike the Cadbury, you won't be able to continuosuly redeem free slurpees because the stickers are on the large cups and the winning slurpees are the super sized ones. Smart.
Extra details thanks to 'moooooooo' => http://www.ozbargain.com.au/node/34012#comment-310727
Nice one.