Fresh fruits and vegetables, you need to eat right, especially while your on the road due to the lack of exercise.
Buy a crap load of fruit and veggies, eat salads, snack on fruit, cucumbers, celery or anything easy to handle while you drive.
Buy a juicer and make some delicious and nutritious fresh juice while on the road. Any ailments you suffer from from obesity-cancer will be healed once you start eating right.