I've never been on carnival :o
Protip: Don't touch anything in the fridge in your room. The cheapest thing is going to be like a tiny bottle of water for $7.
Not true.
I took a cruise, and in my room, the cheapest thing was an ice cream bar for $10.
Then again, I was on some super fancy ass cruise, where a glass of sprite at a restaurant costs like... a lot :c