It's 7-Eleven Day . . . a.k.a., July 11th. So you can get a free Slurpee today if you stop in between 11:00 AM and 7:00 PM. And they also have other deals, like $1 pizza and hot dogs.
Just don't confuse this with Bring Your Own Cup Day, where you can bring ANY container in and fill it up. That one happens in November around Black Friday.
If you show up today, you just get a SMALL Slurpee. So if you walk in with a baby pool and start filling it, you'll just get some weird looks. And they'll charge you for it.