You could always use 91% Isopropyl alcohol or better yet, Everclear 191proof. But they do burn a lot hotter, maybe too hot for a coffee can heater for use in an enclosed space. I'd stay away from Methanol as its much less human friendly than rubbing alcohol or food grade ethanol. Lots of informed ETSers can point out exactly why that is due to its chemistry but I'm not one of them. Rubbing alcohol and Everclear are also 'multiple use' fuels.