For perspective on the bar prices...
Sodas are $1.95 per can, or $2.24 once the 15% automatic tip is added. You can purchase a soda package which allows unlimited fountain sodas (no cans), but I think it's cost isn't worth it unless you drink a lot of soda. It can be a good deal for kids since it gives them some independence when they want a beverage. Plus the price is cheaper for kids than adults, and each person needs their own package (no sharing).
Beer ranges from around $4 to around $6. They have mostly gone to 16 ounce bottles except for those brands which only come in 12 ounce servings.
Liquor drinks and wine are around the same - $6 to $10.
I know these prices are not cheap, but they are comparable to those at a hotel or resort bar. And frankly bar sales (and the other revenue centers aboard) allow the cruise lines to keep the cruise prices as low as they are.
Your onboard spending is really a personal thing depending on your habits and so forth. We generally expect to spend around $100 per day in onboard purchases. However, a trip to Bermuda means less time aboard the ship than on a typical cruise, so you'll need to consider how much cash and which credit cards you'll bring to use ashore. All onboard purchases are charged to your ships account, which you secure at check-in with either a credit card or with a cash deposit. Once aboard, when you buy a drink, a t-shirt, anything, you give them your cruise card to pay for it. Cash is allowed in the casino, and of course for tips if you don't add them to your account.