INFO:
To make a Slurpee, start by shaking an unopened bottle of soda for 10 seconds to build up pressure inside of it. Then, put the soda in the freezer for 3-4 hours, checking on it every 30 minutes to make sure it doesn't get completely frozen. Next, take the soda out of the freezer and twist the cap off slightly to release some of the pressure before closing it again. Finally, turn the bottle upside down and then upright again before pouring it into a glass and serving.
Video: How to Make a Slurpee - wikiHow