Food options- working from your car

Hey everyone so I'm asking this question in behalf of my boyfriend. He's a private investigator and has been for a about a year and a half and he spends anywhere from 6-14 hours a day, 6 days a week in his car. Since getting this job he's put on about 50 pounds and it kills him because before he was very cut and very lean. Exercise is something that's very hard for him to find time for because there are many days where he spends 16 hours just working (driving far, working, writing reports etc.) Anyway in the summer and any time of year where the outside temp is over 75 it's basically impossible for him I bring food unless it's something of the snack variety, and I know this has a lot to do with his weight gain. Now he's a guy so he likes to atleast feel like he's eating a lot because he can eat a lot. Also he avoids anything with added fiber because he has stomach issues from when he was a kid. I'm just finding it difficult to suggest things because I usually think of bars with fiber in about a month he'll be able to start bringing actual food, but I'd just like a few suggestions because I know he wants to be healthier. Any suggestions?