In Hawaii there are several cars that are offered for rent in the economy car category. The Kia Rio is an economy car produced by the South Korean manufacturer Kia since August 2000 and now in its third generation.
Economy rental cars are the smallest size car category. Depending on the rental car company an economy category is going to be a Kia Rio, Chevrolet Spark, Ford Fiesta, Mitsubishi Mirage or similar.
Economy cars can be just two doors or four passengers. They are going to get you every where you want to go. Be sure an economy car is large enough for the passengers in your party and luggage you are carrying.