>"Within 2 hours, I had bad stomach cramps, dry heaves, dry mouth,
eventually diarrhea..."

benzoic acid (material safety data sheet
http://www.jtbaker.com/msds/b1356.htm )
states that large oral doses may cause abdominal pain,sore throat,
nausea and vomiting. possibly, because of all the sugar, there is a
larger amount of benzoic acid in the solution than other foods, or,
there could have been a mistake in making the solution with a high
dose.

A search of the amer. acad. of pediatrics website http://www.aap.org
will confirm that Sorbitol is the main fruit sugar found in most
fruits except citrus that causes problems. A common symptom is
diarrhea (also found in chewing gum and laxatives).
The MSDS search http://www.jtbaker.com/msds/dO832.htm states also for
Glucose that extremely large doses may cause gastointestinal
disturbances.

Your ingredients list also had natural flavors, but I bet that's from
the orange flavor. Tho I remember that drink to be strongly orange
colored, too, and the color is not listed on your label.