Irn-Bru's main ingredients include Carbonated Water, Sugar, Citric Acid, and a unique blend of Flavourings containing Caffeine, Ammonium Ferric Citrate (a trace of iron), and Quinine, plus sweeteners (Aspartame, Acesulfame K), Preservative (Sodium Benzoate - E211), and Colours (Sunset Yellow FCF, Ponceau 4R) for the original recipe. Variants like Xtra and Sugar Free use sweeteners instead of sugar, while Irn-Bru 1901 uses Quillaia Extract for foaming and no artificial sweeteners.