Fantastic Freebies: Slurpee at 7-Eleven: Today only!
No coupon needed -- just show up and ask for it. But be careful: Slurpee's are among the least healthful things you can possibly put in your body (other than heroin, etc.). A 7.11 ounce Slurpee has about 23 grams of sugar (Nutrition information), 50 milligrams of caffeine and not much else.
For a lower-calorie alternative, try the Crystal Light Slurpee, which has about 1/3rd the calories.