I think you can buy an alcohol content tester commercially but i recently ran into a post on another forum about how to do it in a pinch. It's worth looking at:

TTo save some bucks I used an olive bottle for my ethanol tester because it is tall and skinny just like the tester.

All you do is make a mark on the bottle maybe a half inch from the bottom and fill w water to that point. Then add gas to fill most of the bottle and shake. Let is sit for a minute or so and>>>> If the gas has ethanol it will combine with the water and the "water/alcohol" level will now be higher. Simple.
I have a station that is very good about no ethanol but one can never be sure.
Glen

To make it even easier just fill with gas and put a couple drops of food coloring in it. If it has ethanol the food coloring will mix with the gas, if no ethanol it will just sink to the bottom.

I've done it both ways but the food coloring method is really easy and any water-based food coloring works.

With the water based food color method, after you add the food coloring do you need to shake to mix, or just add the drops and watch?

Other then when I fill my 300 gallon home tank (and then I trust my fuel distributor who also uses mo gas in his C-172 and it for sure is ethanol free in bulk) I never check for ethanol. If I'm on a xc and need mo gas, I may ask the locals, depending on what state I'm in, if any stations in town have real gas, other wise I just get whatever fuel is available as the Rotax really can't tell the difference, at least I can't. Though I am still not comfortable with keeping E-10 in my bulk tank, I just don't see any problems with using it from time to time, especially when it's burned up a day or so after buying it. I credit Emsfly with helping me get over my E-10 paranoia, as he had been using it in California long before we had to up here.

You can shake it if you want but when you first do the test it's more than obvious