I'm not sure how they make the distinction, but it seems that anything that is a "logo-ed" product or pre-prepared costs extra. This may be an over-simplification, but it seems to be generally true. For instance, anything you buy already in a sealed container will cost extra, e.g. sodas, bottled water, wine; whereas juice, tea, (most) coffee, and "tap water" are included. All alcohol will be extra (and quiet a bit extra
You definitely won't be left without food or drink, but the premium brands will cost extra, e.g. Hagan Daz vs. bulk ice cream, espresso's vs regular joe.
Kelly, not at dinner, yes and no. <VBG> Soft drinks are extra except in the dining room onboard RCI. Most other lines charge all the time for soda. Bottled water is always extra. What you may wish to do is just bring your own or just a bottle or two and then fill it up with water from the ship as it is mostly distilled and quite pure. Fruit juices are almost always available in the self serve areas 24/7 and you can of course always order them through room service.
I thought it was goofy that you had to pay for a milkshake in Johnny Rockets, yet soft serve ice cream and milk are both free. Also the fact that right next to the Sprinkles soft serve stations, they are selling ice cream sandwiches out of a freezer. And then the free sodas at dinner (but only dinner) paradox.
I'm not complaining, and rather like not having to pay for sodas from the bar at dinner like you do on CCL. But, it is an odd line they've had to draw. You can order as much filet mignon and lobster tail as you want, but a bag of chips from the general store will cost you a couple bucks- To that, I say bring on the surf and turf and keep the chips!