To start, here is my farm. (sorry about the quality, I am not good at making gifs)

So as I am sure we all have a single player world where you can build and test ideas before making them on survival and I was on mine trying a new concept for a sugar cane farm. My inspiration came from here. I wasn't really trying caring for resource friendly. I just wanted to try something new, and really this farm does not cost too much. It can be expanded much larger than you see in the gif with not much more resources at cost (Although I wouldn't recommend expanding it past your chunk render distance). Of course, I also increased the tick speed to give a more dramatic presentation, but the efficiency is not so bad. A full harvest if all sugar cane is grown 2 high should yield exactly 6 stacks, but I lose usually ~20 on every test i did. You might wonder about the sugar can that simply drops on the sand. There is a minecart with a hopper under each section of sand that picks up any sugar cane that drops and dispenses them into a line of hoppers which feed into a chest. You may also think that would cost a lot of iron/gold but this is where your own minecraft morals come in. There is currently a rail duplication glitch in 1.9/1.10 which i have been using because of my own reasons. If you do not like exploiting glitches in the game, then go ahead and mine away! I haven't really tested how much sugar cane you get per min or hour yet but when I do, the test will be on a much larger version of this farm. What I like about my design is that it uses a lot less pistons which makes it a little less heavy on iron. Anyways, tell me what you think and how I could maybe improve it?