I always make sure I have healthy, high-fibre snacks in my car that are not worth more than, at most, 2 Weight Watcher Points. That gives me a go-to something when hunger strikes and I'm stuck in traffic, or whatever.
These snacks are usually protein bars or apple slices or a banana. I love the All Bran Bars, but you can't get them in the US. Water is important, too, to have on hand. But DON'T leave the plastic bottles in the car. They become carcenogenic, according to Melissa Etheridge!