The Rarotonga restaurant scene has improved in recent years and you now have a good choice. A few restaurants are found on Aitutaki, but none exist on the outer islands. When ordering, keep in mind that an "entrée" is actually an appetizer and not a main dish. Garlic bread seems to appear on every menu regardless of cuisine!
By law all bars are required to close at midnight, except on Fridays when they can stay open until 0200 Saturday morning. On Sunday no alcohol may be sold at grocery stores and even licensed non-hotel restaurants aren't allowed to serve alcohol with their meals until 1800 on Sunday. (Hotel restaurants can serve alcohol anytime.)
Wine is expensive at restaurants, because of high import duties, and drinking alcoholic beverages on the street is prohibited. You'll save a lot on meals if you stay at one of the many motels and guesthouses offering cooking facilities.
Rukau is Cook Islands palusami, made from spinachlike young taro leaves cooked in coconut cream. Ika mata is marinated raw fish with coconut sauce. Locals insist that slippery foods such as bananas lead to forgetfulness, while gluey foods like taro help one to remember. Dogs are sometimes eaten by young men on drinking sprees.
(Turn to the Atiu section for information on "bush beer"—called "home-brewed" on Rarotonga and Aitutaki).
Tap water in the Cook Islands is not chemically treated and it's safer to boil it before drinking. Otherwise drink bottled water or beer.