We are addicted to Diet Coke and bottle water and would drink ourselves out of house and home if we didn't bring it on board. This is what we do.
We have two suit cases, large and medium. We put the medium into the large and then pack the medium full of our clothes, etc. Once we get into the port , we hail a taxi to the ship and ask the driver to stop at any near-by grocery store or convience store. (as a side note, we always buy the 20 oz plastic bottles, they are great to have in your pool bag on deck or take on shore with us). We then take the medium suitcase out of the large and fill the large with the soda and water and check it through at the ship.
The cab costs only a little more than the transfers plus we're not packed on a bus with all the other people (not to mention waiting for all the other flights to land so that they don't loose money sending the bus until it's over packed) :-) and have some flexibility and then we can buy all the water and soda we want.
Our cabin stewart has always been generous with the ice, we keep a few in our ice bucket so that we always have them cold, and you can get cups of ice anywhere on the ship.
Coming home now we have all the room we need in our suitcase to pack all the stuff we bought during the cruise -- you know how your suitcase always seems to shrink.