We left our sodas in the box and carried it onboard. My son looped the handles of the plastic grocery bag over his wheeled carryon.
Our first cruise we packed it in the suitcase inside an XXL ziploc bag. One can burst, but the bag contained it. After that experience, I would not pack anything breakable in checked luggage.
If you try to take beer in a carryon, it will be taken and thrown away. We saw piles of beer cans next to the first security entrance.
We put the 12 pack we brought once in the checked luggage. The next time we brought fewer so just brought them loose. The 12 pack fit nicely in the checked suitcase, but because of the weight had to put all clothes to fill up that suitcase and put the things that weighed more in the carry on.
We've always packed soda in either a carry on bag or one time actually put it in a soft sided cooler and I carried it on by the shoulder strap. When the steward came to service the cabin, he would refill the cooler with ice so I always had a cold diet coke waiting for me.
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.