Ok, this came to me in a dream last night so if it sounds like nonsense, carry on and pretend you didn't see it. I live in Colorado so fresh ingredients off the tree are out of the question but the local Whole Foods has Coconut water, coconut sugar and dried coconut. I'm thinking the water probably has preservatives in it which might not play nicely with yeast but homemade rice milk could be a possible substitute. Pretty sure that just involves mashing/pureeing rice in water. Then boil with chunks of dried coconut and add coconut sugar? What type of yeast would work well? Normal brewer's yeast, wine yeast? I don't even know where to start with sake yeast.
Anyway, let me know some thoughts. I'm going to head over there today and pick up some ingredients. They even have gallon apple juice jugs which make great test fermenters