I believe the only free restaurants are The Windjammer and the dining room. Drink costs vary. I don't drink that much, so maybe someone else can answer that.
If the ship has a Royal Promenade, Cafe Promenade has some free items, including Seattle's Best Coffee.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas