Subconsciouses are odd
Mine just filled my brain with the inviting image of a nice cool glass of water. I was on the point of getting up and going to the kitchen to get one, when I noticed I had one already – and then I felt disappointed.
I can only assume that what my subconscious really wanted wasn't the water itself, but the getting-up-and-stretching-of-legs involved in getting it. I wonder why it didn't just say so.