On all cruiselines I have been on there has been free coffee, hot and iced tea, lemonade and sometimes fruit juice and hot chocolate.
On our first cruise 5 years ago-we could get cola free at the lido deck buffet but if we got this in a lounge we paid for it. That was the only cruise though that I saw colas at no charge.
I usually just drink plenty of tea, fruit juice and lemoade and occasionialy order a cola if I am somewhere like the paino bar. I try not to drink a lot of colas anyway as they are so bad for us so it is no hardship for me.