Soda is an added cost on most all cruise lines (cept high, high end ones).
A coke on HAL back in June was $2.50 plus 15%. Most of their ships offer a
'pop card'...a one time fee for all you can drink for the whole cruise. The
fee varies with the length of your cruise.

Coffee, tea, juices, lemonade, water, hot water/tea are all included (no
extra charge).

Anything with alcohol is extra except for a couple of hours for the captains
reception. (complimentary drinks, often rather toothless.)