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Start scouring your home for the biggest cup, bucket, or bin you can find. On Friday and Saturday (August 19th and 20th) 7-Eleven is continuing its 50th birthday celebration by offering Slurpees of any size for $1.50, as long as you bring your own container, whatever that may be.

Some clever examples? A plastic Halloween Jack-o-Lantern, hollowed out watermelons, and various sand castle molds. If you need inspiration, try following #byocupday on Twitter and Instagram. There are restrictions on what you can bring, though. After previous years’ participants got a little too creative—think kiddie pools, toilet bowls, and sleds—containers must now be no more than 10” across. There’s even a cardboard cut out hole by the machines to measure.

7-Eleven is also looking out for your health, by declaring that containers must be food safe. On their site this plays out as no electronics or old shoes, although we’re hoping you wouldn’t want to do that anyway. There can also only be one cup per customer.

If you’re truly a Slurpee addict, consider joining the 7rewards program while you’re at the store filling up. Download an app, and after buying any six drinks, the seventh is free.