Pour beverages into your tupperware. Make sure your tupperware is freezer safe!
Squeeze the juice of one lemon into the container.
Freeze for an hour.
Scrape with your fork.
Freeze for another hour then scrape with your fork.
Freeze for another 30 minutes then scrape with a fork - repeat for the next 2-3 hours. Please note that depending on your tupperware size the ultimate length of time it will take to freeze will differ. But if you scrape the granita every 30 minutes you won't risk it totally freezing over.