We brought a 12 pack of gingerale(I am pregnant) and coke onboard the Prinsendam over our 2008 Christmas cruise. We had the packaging in plain sight so our room stewards knew they were not from HAL stock and did not charge us for the empties. We had them with lunch, or in my case when needed above that, and I took a gingerale to the DR on New Years Eve to have as my "champagne". No problems encountered in doing so, and no one from HAL ever said a word. Certainly a lot less expensive then buyng pop onboard the ship.