I always carry a snack in my bag. It gives me better options in emergency situations.
Pretzels and individual peanut butter packets (I buy those
online.)
Soyjoy bars
Homemade trail mix (because the premixed variety has way too much dried fruit) - soynuts, almonds, walnuts, pumpkin and sunflower seeds (all raw and unsalted) and just a bit of either dried plums or apricots.
Slim Jim Beef and Cheese Sticks (I also buy these
online.) Not exactly healthy, but it's an easy-to-transport snack