Get a 44oz cup from Quick Trip (Filtered Water - Crushed) and FILL it to the top, then fill it most of the way with Sprite. Take it home and freeze it, then break it up.
Another fun recipe is to fill Ziplock baggies a little less than 1/2 full, then lay them flat in the freezer, then break the "ice plate" up with a spoon.
****CAUTION - THESE ARE ADDICTIVE RECIPES!*****