its possible, but will require some of your time and
effort.
you can prepare food such as sandwiches, these can be eaten,
anywhere anytime. or if you have access to a microwave, you can
bring along stuff and heat in the microwave. I myself take
sandwiches most of the time, you can prepare them in the morning
before you leave, or the night before, what ever is best for
you.
eating healthy is not easy, or else much more people would do it,
the rewards are well worth it though 