The Slurpee Scheme is used to get free things with the purchase of any Big gulp.

First you walk into a 711, then you grab yourself a couple things that will fit inside of the cup without taking up more than 4/5 of the cup, then you Grab a Big Gulp or other non-See through cup and put your stuff in the Cup(Make sure you don't get spotted) then proceed to fill the cup up.

It works a lot better if you have a refill too.