I would guess you would most likely have to buy cups of ice, with or without the soft drinks, from the food vendors. Large, movie theater sized cups were $3.35 this year. For $2.95 you got a considerably smaller cup.
The heat can be nearly overwhelming on any particular day. While ice cold water would be refreshing I think just staying properly hydrated might be the goal on those days.
A hydration pack, Camelbak or equivalent, might be an option if filled with ice. Not sure if the effort of carrying it around all day would outweigh any benefit but it's a thought.