Darn,
and I was hoping you could "Make" fuel just by shaking it

You have to add water with that method. The alcohol mixes with the water, that's when you see a change in the level of the fuel between the water layer and the fuel floating on top.

Whoops! You're right. I'm re-reading the testing method.

A narrow tall container works best.

First Fill the container about 10% full with water (no, leftovers from the pee bottle don't count).

Mark the water line.

Then mostly fill with fuel, cover, and shake.

Let stand 5 minutes

If the water is higher than the line, it has alcohol.