Banana-flavoured beer, which I bought without reading the label on a train to Kunming. I forget the brand, but I always read the labels now. A nasty surprise when you're just expecting the ordinary local beer. Think banana flavouring flavour. And then add the hoppy taste of beer. Ewwww.
Followed by Guang's Pineapple-flavoured beer in Guangzhou, which I bought because it was there on the menu. "Pineapple beer?! Damn that sounds awful... I'll try it."
Even Snake Gall Bladder Wine (spirits really) doesn't compare to those two, and that's all pond scum green from the gall bladders in it.