Irn Bru tastes like Irn Bru man, nothing else, they ruined it a bit since they took the sugar out of it, but the Irn Bru Xtra is very nice, tastes the closest to the original.
End of the day, Irn Bru is actual gods pish it's that good. I did see once in a video some idiotic Americans saying it tastes like Cream Soda, boggin man it tastes nothing like Cream Soda.