We always bring small bottles / cans of soda, water, & Spicy V8 As well as alcohol and no one has ever said anyting. I think they make the rule hoping most folks will observe them, but from what I have seen onboard ship, short of homicide, RCCL does not enforce rules.
Queen Mary 2, Canada
Enchantment, Western Carribbean
Century, Western Mediterranean
Jewel, Eastern Caribbean