well, you have to provide free water and ice or you could have a public relations issue. Someone has heat exhaustion or gets really sick and you didn't provide water or ice it can be a bad deal.
There might even be a law.. but not sure.
I think it’s an either/or situation. They have to provide water OR ice, not both. I would think water would be the better option, since it can take time for ice to melt.
Edited to add that it is law in most states, but not all. However, it is a law in Florida.