Yes i have found if you have drink coupons you can get any drink you want. You just order up and give the bartender the coupons. I think the best deal ,as far as prices go, is to order the drink of the day, usually only $3.95 each and usually a rum drink. Also you can order a bucket of beer, which is cheaper than getiing them one at a time.
I've never used the drink coupons. I think the drinks-of-the-day are around $6 in the souvenir glass. Here's a hint...by your first drink in the souvenir glass and reuse the glass. Your refills are cheaper and you get more booze than buying it in a regular glass.
I don't remember how much soda/pop is on the ship. I want to say $1.50-$2.00.