We have only carried on soda once since there is usually just the two of us. We used a soft-side cooler on wheels to carry it on (no ice) and put it on our balcony. I looped the handle of my tote-bag over the handle of the cooler and just rolled it all onto the ship. I kept a few cans at a time iced down on the balcony, but decided it was really too much trouble to do it again. If I were traveling with children, I would probably do this, but not just for the two of us.
We don't have any problem drinking the ship's water. I usually add lemon or a crystal light pack for a change of pace.