I posted this a couple of months ago. You can also do a search for coffee cards under the Find tab and get other people's input on the coffee cards. My post was:
"My husband just bought the prepaid coffee card, I believe it was $25.00 for 14 or 15 coffees. You can get lattes, mochas, etc. at certain bars only. I think there were 3 bars on our ship that accepted the card. Also, if you want regular coffee, at some bars they will charge you. You can always get regular coffee up at the buffet for no charge."
Also, Princess does have soft drink cards. We paid $39.50 for our 10 day cruise.