Here is their Grape Candy flavor, which is actually pretty awesome!
The chemicals are:
Methyl anthranilate, CAS number 134-20-3
Ethyl butyrate, CAS number 105-54-4
3-Hexen-1-ol, (Z)- , CAS number 928-96-1, can't find much on this, as its Wikipedia page is a stub, but it seems to be some sort of pheromone-type thing, the external MSDS linked from Wikipedia just states "if inhaled, move to fresh air" when dealing with pure unadulterated amounts of the stuff..... so diluted to 1-10% it probably isn't horrible.
Benzenemethanol, CAS number 100-51-6, also known as benzyl alcohol, slightly toxic on consumption, irritant, probably the only thing to worry about.
Other ingredients in a juice made with this flavor would be Propylene Glycol, Vegetable Glycerin, Water, Nicotine.
Grape candy flavor is probably a lot easier to replicate than other flavors that require more chemicals, but this just goes to show that flavors can contain few chemicals and that it's possible to find exactly what is in a lot of flavorings through MSDS snooping (if available), and in most cases, even the more insidious chemicals in the flavorings are just irritants (benzyl alcohol seems a little scary but when it comprises a couple percent of a juice by volume, and someone consumes even 30ml of that juice a day, they are ingesting maybe a milliliter of the stuff tops per day, which is probably within safe limits). Diacetyl, diketones, etc aside, a lot of juices are pretty inert and just contain a lot of chemicals used in perfumes/food/etc and that's about it./