Fill various sized bottles and jugs half full of water. Place bottles (not gallon jugs) so that they lean (keep stable) to one side while freezing (without lids). Keep gallon jugs upright (also no lids). When ready to use fill with fresh water and screw lids on snuggly and you're all set to go!
Depending on whether you're using at home or on various length trips you have an icy cold drink that stays colder than fast melting ice cubes. The angle results in greater surface area of ice and the thinner top of ice on one side melts a little faster to provide additonal drinking water over time!