I tried barley tea whilst in Korea. If you can imagine tea that tastes like it's full of wheat you'll get the idea. Apparently it's very popular here. It's much like green tea in China, you get used to it after a while and even start to like it.
I also tried a local corn iced tea that is apparently very popular. Imagine chilled green tea that has had popcorn soaking in it for a while and that's pretty much what it tasted like. Not unpleasant, just strange.