Yes. I want the 2017 recipe, not the 1901 recipe.
The 1901 recipe has 11g sugar per 100ml. Also it lacks caffeine.
The 2017 recipe had 35g sugar per 100ml.
The 2018 recipe has 4.5g sugar per 100ml.
The sugar tax is £0.18 per litre for 5-8g sugar per litre, and £0.24 per litre for >8g sugar per litre.
Irn-Bru has many price points depending on form factor and location, but a 2 litre bottle today typically costs £2.10. The sugar-free variant costs the same. If the full sugar tax applied, it'd cost £2.68 (22.8% higher price).
Coca-Cola is so expensive with the tax, they don't even sell it in 2 litre bottles anymore, just 1.75 litre bottles. Coca-Cola "Original Taste" is £2.55 for 1.75l (£1.46/l) while Coca-Cola Zero is £2.15 for 2l (£1.08/l), a difference of £0.38 per litre, of which £0.24 is sugar tax.