What is the healthiest fruit? How about vegetable? Food item in general?
Individual food items aren’t healthy or unhealthy. The combination of the foods you eat make up a healthy or unhealthy diet.
As far as liquid refreshments go, I think Beer must be very healthy. I drink a good bit of it, and my health couldn’t be any better than it is.
ETA: just saw Telemark’s comment. He is correct. Please add Pizza to my recommendations for perfect health.
Well not if you keep drinking all that beer it can’t. 
I think I heard on NPR a long time ago that cabbage gives you the most nutrients per dollar. That is, there are other vegetables that may contain more nutrients, but they’re fairly exotic and expensive. Cabbage is pretty cheap and pretty nutritious.
A McDouble gives you the most nutrients per dollar. A cabbage is basically just water. It has some vitamins, sure. But those are micronutrients. Macronutrients is where all the live-sustaining energy is at, and you aren’t getting very many of those from the cruciferous veggie family.
I think this article is a good reference. The 8 foods it lists are spinach, yogurt, blueberries, black beans, tomatoes, carrots, oatmeal and walnuts. It gives info on benefits, sources, and substitutions.
Beverages like coffee, green tea or whey protein can have various health benefits.
As far as fruits, pomegranates and blueberries supposedly have health benefits. Unsure what fruit is the most healthy though.
Who are you gonna listen to? Me with pizza & beer, or those guys with their cabbage and black beans?
I think I can guess which one they might prefer to visit. 
For those of us on a kidney-friendly diet, everything is different. My healthiest foods are:
Red bell peppers
Cabbage
Cauliflower
Garlic
Onions
Apples
Cranberries
Blueberries
Raspberries
Strawberries
Cherries
Red grapes
Egg whites
Fish
Olive oil
Not only is it a matter of what combination of foods you eat and not just of a single food, but the best combinations (note the plural, there’s unlikely to be only one possibility) aren’t going to be the same ones for every person.
Eatthis is a site selling things. You cannot trust them to give out good information.
American Cancer Society, among others, recommends that you eat a variety of foods.
Firstly, different fruits and vegetables provide different (micro)nutrients, and they are not interchangeable. Furthermore, the science of nutrition is still fairly new. For instance, Lycopene was not a well known nutrient until sometime in the 90s.
Vitamin research was only started in the early 1900s, so just over 100 years? And IMO, the definition of vitamins is fairly strict - to be a vitamin, there has to be a disease recognized to be caused by the deficiency of the vitamin. And as I understand it, except for a couple of vitamins that are not as easy to get so are commonly added to the food supply (such as Vit. D*), the only way that deficiency is found is through people who are unable to consume food normally, such as people in comas.
Recent research has been looking at anti-oxidants, which are purported to solve everything from the heartbreak of psoriasis to male-pattern balding** But recent studies show that too much might actually increase your risk of cancer.
If you’re looking for a rule of thumb, the one that fits best with the information I’ve read is “The more colorful, the better”. Considering that at least some of the micronutrients in question (I’m looking at you, beta-carotene and lycopene) are also the substances which are giving the fruits and veggies their color, I think this is a good way to choose your fruits and veggies.
*Iodine is also added to salt, are there any other nutrients that are commonly added to food?
** don’t get your hopes up
weeelllll, if by “cabbage” you mean the typical white or red heads of cabbage, then no, they’re only slightly better than iceberg lettuce (which is basically crunchy water.)
if by “cabbage” you include all of the cultivars and variants of Brassica oleracea (of which white and red cabbage are members,) then they’re highly variable. Collards, kale, broccoli, brussels sprouts, etc. are loaded with micronutrients.
Green grapes aren’t healthy?
Not as healthy as red grapes, for someone with kidney disease.
I expect we’ll all be hearing from the cabbage-and-black-bean guys whether we want to or not.
Leave it to the health nuts to toot their own horns!
I didn’t know that. What’s the reason why?