if it was me, I would one fill tank with fresh TREATED fuel
run treated fuel for a good 5 minutes and then shut motor off and LEAVE as is
BUT Then when going to re start atv after a yr of sitting, I would drain everything, pull and even clean carb
my reason is, there are seals and gaskets that if you leave them sit DRY they can fail, faster IMO then if full of fluids!
NOW< if you really WANTED to use NON ethanol fuel, like said above, LOWE"s HOME DEPOT and like places sell it, in a metal can,, would NOT be cheap to buy to fill the tank, but you should b able to get ti there in with where they have lawn mowers and chain saws!
I would also be plugging up the exhaust with an exhaust plug, adding some moth balls to air box, and pulling battery out of atv and kept indoors on a tender
I MIGHT even pull spark plug and spray down hole with some WD 40 or like oil, to help make sure things there stay free!
also I think I would jack atv up off the ground to relieve tires from getting flat spots opt cracks in side walls!