One who is traveling:
One who is traveling during the holiday of Sukkos through in an uninhabited area and is sleeping and eating in the fields is exempt from building a Sukkah. However when he arrives to a town, even a town of gentiles, and he desires to eat or sleep there, he must build a Sukkah if he has time to build it prior to the normal time one eats and sleeps.
One who is traveling for a Mitzvah: If one is traveling for a Mitzvah purpose, such as to redeem a captive or to greet his Rebbe, then he is not required to dwell in the Sukkah during his travels even if he is in a inhabited area that contains a Sukkah. However if the Sukkah is near him, and he is able to dwell in the Sukkah without any impediments being caused to the fulfillment of the Mitzvah, then he is to dwell in the Sukkah.
May one travel for leisure purposes, like going on a overnight hike if there will not be a Sukkah available during their stay?
One may not do so. One may only travel through areas without a Sukkah for business purposes or other necessary purposes.