What are the main flavours/aroma compounds of the Scottish soft drink "Irn-Bru" (Iron Brew)?
AG Barr answered that a while back in releasing the fact the Ammonium Ferric Citrate was a key ingredient in flavouring the drink. That, however, is not the full story.
If my memory serves me correctly, UK food labelling regulations allow the catch-all term &quot;Flavourings&quot; to allow a manufacturer to maintain intellectual property rights for their recipe.
Other than that, the ingredients most-to-least (apart from the actual percentages which are protected under the same legislation) are as follows:

Carbonated Water
Sugar Acid (Citric Acid)
Flavourings (Including
Caffeine, Ammonium Ferric Citrate &amp; Quinine)
Sweeteners (Aspartame, Acesulfame K)
Preservative (E211) Colours (Sunset Yellow FCF, Ponceau 4R)

(Contains a source of Phenylalanine. Sunset Yellow &amp; Ponceau 4R)
https://www.agbarr.co.uk/our-brands/irn-bru/#:~:text=Each%20Serving%20Contains-,Ingredients,Contains%20a%20source%20of%20Phenylalanine.