My dad rides a customized engine in a 2002 Harley. With the huge power-to-weight ratio that he now has, he gets 50mpg regularly - even better with a tail-wind. He can haul enough gear in the trailer and tour-packs to enjoy 2 weeks without seeing "civilization" - as long as the tank can be filled up.
The only problem is that the tank is good for about 3hrs of driving time - or - 300km between fills. His GPS helps him locate fueling stations along his route when he is on the long tours.
There are a wide variety of motorcycles out there, with various capabilities. Average mileage is often around 45mpg, and tanks usualy have 3 or 4 useful gallons. A KLR650 has a 6 gallon tank, which is one of the larger stock ones, and there are a multitude of add-on tanks for long-distance riders or racers. I personally look forward to a 150 mile range, it forces me to stop and rest and keep my head fresh. Motorcycle requires complete attention, unlike many cars.
Soda can, no problem. Coffee can, maybe a problem. Rule of thumb on roadkill (swerve, or hit it?) is if you can eat it in one sitting, it's okay to run over. Any bigger, try to avoid.
Seriously, riding is epic fun, but it requires a minimum level of skill, dexterity, and total concentration. No zoning out, that's what makes for dead riders. And nobody's looking out for you, and you don't have a protective shell. Do at your own risk, take the MSF course, and be humble.
I ride ( a lot!) and have riden for many years. My larger bikes (1000cc and up) get about 45 mpg. The mid range bikes (350cc to 1000cc) get a little better mileage but the tanks get smaller quicker. The small bikes get incredible mileage but tend to have very small tanks...for this forum, a 150cc to 250cc bike (dual sport type) fitted with a baja style tank (available aftermarket) gets the rider through many areas, is streetable and gives 200+ mile range. Also the paris/dakar style and GS (BMW) style bikes are outstanding for light off road/single trak trails. I think having a small bike and a mid range would be a good idea for "preparedness".