In Breaking Bad S02E09, Walt and Jesse go to the desert to cook meth and they drive approximately 15 miles/24 km down a dirt road. Midways cooking, they realize the car battery is dead, and manage to kill the generator and spill their drinking water. At this point I assume they could make the walk. The next day they spend hours of hand cranking the generator in the desert sun to no avail. In the end they make a DIY battery to start the RV.

So if the DIY battery failed and they waited until the sun set that day, after ~30 hours without water, would it be humanly possible for them to walk 15 miles? And could meth be of help?