i agree with bubblej that you do need to plan. and yes, planning to be busy and on the run is what you need to plan for. they make a ton of shelf stable options that you can keep in your bag. yes, you'll have to do some reading at the grocery store to pick them out. you should also keep a list of these kinds of items at the grocery store, so you can run in an grab the perishable ones as needed [it's at least as fast as running to get fast food]. you can find applesauce or pearsauce in individual half cup servings, fruit cups in their own juices, cup of soups [nile, health valley and dr macdougall's have some great flavors out there: lentil curry, chili and the black bean has 13 g fiber in one of those cups!], jerky, nuts, granola, granola bars, shelf stable individual nut butter and hummus packets, dehydrated fruits or veggies and that is what i can think of offhand. then you have yogurt, sushi, parfait cups, hot soups, subs, hardboiled eggs, hummus, salads, precut fruits or veggies, and deli meats and cheeses for the perishables that you can run in and grab while you are out on the go.
then you have fast food places. odds are you have at least a few that you prefer to go to. so make a list of those places. then spend some time on their website working out an option that's a little better for you than what you usually get. it doesn't have to be the perfect option just yet, you just want it to be a little lower than your usual in the things that usually get you off track [probably calories and fat]. as you find new options that you like the taste of and fit in your diet better [and yes, i use the primary definition of diet which is simply what one eats], you can scale back to an even better option then.
-google first. ask questions later.