Museum of Science and Industry

Ingredients:

Water

Even pure orange juice (which SunnyD most definitely isn't) would be mostly water once all the orangey stuff had been removed. 

High Fructose Corn Syrup

Sugar, basically.  Corn starch is most commonly broken down by enzymes to create the simple sugar glucose.  By using slightly different enzymes during the process, manufacturers can turn some of that starch into another simple sugar, fructose.  Market research has shown that most people like the taste of syrup that's 45% glucose, 55% fructose (hence “high” fructose).  Thanks to HFCS, Americans now consume 120 lbs combined of sugar and HFCS per capita (in 1973, before HFSC was mainstreamed, it was 102 lbs).

2% Or Less Of Each Of The Following: Concentrated Juices (Orange, Tangerine, Apple, Lime, Grapefruit)

See, there is some juice in Sunny D.

Citric Acid

Citric acid is actually pretty good at killing the flu virus if you spray it directly up your nose.  Its presence here is probably to add some citrus-y zing to the flavor, and/or to act as a low-level preservative.

Ascorbic Acid

Better known as Vitamin C (not the singer).  Since primates (and, for some reason guinea pigs) are the only mammals that do not make their own vitamin C, we need to get it from outside sources.  Lack of this vitamin can lead to scurvy, a disease marked by muscle weakness, bleeding gums and loss of teeth, and general confusion – it's a lot like suddenly turning old.  Vitamin C is also a powerful antioxidant, which can neutralizes some of the damage that leads to signs of aging such as wrinkles.

Thiamin Hydrochloride (Vitamin B1)

A water soluble vitamin that helps the body digest carbohydrates, such as all the high fructose corn syrup you've just ingested. Much of the mental degradation of people with severe alcoholism, as well as the nerve problems of diabetics, are caused by lack of thiamine.

Modified Cornstarch

Regular cornstarch, when heated, turns into a thick, cloudy gel. Modified cornstarch turns into a clear gel with the consistency of mucus.  Why would you put something like that in Sunny D?  One reason might be to emulate the “mouth-feel” of real orange juice, which has a thickness and a texture you can't get from water and 2% juice. So how do you modify cornstarch? Simply soak the starch in a mixture of alcohol, acid, and phosphorus oxychloride.

Canola Oil

Also added to help with the texture of the drink.

Sodium Citrate

A common component of soft drinks and spreadable cheeses, sodium citrate is most likely added here for its slightly sour taste.   In high doses it's also a laxative, and can be used as an anticoagulant for donated blood. In addition to its taste, it is probably used as a mild preservative.

Acesulfame Potassium

Just in case HFCS and real fruit juice aren't enough, this is an artificial sweetener 200 times as powerful as table sugar.  Unlike aspartame, it is totally artificial, so after it passes your taste buds your body has no idea how to metabolize it.  It is nearly always excreted unchanged in the urine.

Neotame

An artificial sweetener made by the Nutra-Sweet people.  Aspartame (the original Nutra-Sweet) has one major drawback: people suffering from phenylkeotnuria (PKU), a disease which prevents them from metabolizing the amino acid phenylalanine, ran the risk of extreme side effects if they ingested it.  Neotame is supposed to block the release of phenylalanine, making it safer for PKU sufferers.

Sodium Benzoate

All these sugars taste great, but they have one drawback — they can serve as food for mold and bacteria if left around too long.  Sodium benzoate (the salt of benzoic acid) is used as a preservative – only about 0.1% is enough to guarantee that a product has been properly preserved against microorganisms.