I was on the Enchantment last summer, and drinks worked this way -
Water, Tea, Coffee, and some fruit juice (apple and orange at breakfast only I think) were available pretty much anytime the Windjammer was open for meals. There were only a few hours each day where it was closed off. There was also a snack area open in the Solarium during different parts of the day - also with beverage machines. I didn't notice until late in the cruise that there was a separate drink area in a little corner just outside of the Windjammer that appeared to be available all hours.
So in summary, those beverages are available all hours at no cost.
Sodas are never free - apparently not even at dinner. However, you can purchase a soda card the first few hours of the cruise that gets you unlimited sodas and certain juices for the length of the cruise. They are $4 per day per child, $6 per day per adult. Only buy this if you think you will drink a lot of soda. We bought it and came no where near that cost. The sodas were either $1 or $1.50 per beverage. So at $6 you would need to drink four a day every day just to break even.
I don't like that much soda.
Hope this helps.
Enchantment - August 2005