1. Is there a grocer near by? Head to the produce section and get a bag of pre-washed and chopped lettuce. Then head to the canned goods and get a poptop can of black beans, or better, go pick out some salsa that has beans built in. Add some canned chicken if you want to, and if you feel like it, get a bag of gf tortilla chips. Drain (and rinse, if you can) the beans, combine with the lettuce, top with salsa, and Voila! Taco salad! I've even seen individual servings of guacamole in refrigerated sections which would just be icing on the cake, so to speak. (This, of course, assumes you have a plate, or at least a fork, though in a pinch I bet you could open the top of the lettuce and add the other ingredients right in the bag...)
2. This is a two-fer: Nuts and/or raisins. Nuts are high in healthy oils and protein and they can really stave off the hungries. Check the ingredients though; I once started chomping on a bag of airline peanuts only to discover that they were not gluten-free. They can also be super high in salt, so mix them with raisins for your own on-the-go trail mix. Raisins are sweet and filling and can cut the overly salty nuts.
3. Fruit. There are fruit trucks and stands on every other corner in Philadelphia, but maybe it's harder where you are. But even convenience stores are carrying apples and bananas these days.
4. Kind Bars. They are appearing in more and more convenience stores. They are gluten free and really tasty (though they have enough calories to be the better part of a meal but not enough food to feel like I've had lunch.) Drink a bunch of water to help you feel fuller.
5. Hummus and baby carrots. If you are still at the grocery store, check out the produce section for hummus. Add a bag a baby carrots. You are golden.
6. Still at a decent-sized grocer? For a sweet treat, head to the frozen aisle and get a bag of mangos or blueberries (or your frozen fruit of choice, but I find that this doesn't work very well with whole strawberries). Pick up a bottle of seltzer. Make yourself a fruity fizz! The frozen fruit chills the seltzer and the seltzer helps thaw the fruit.
7. Peanut butter! Also readily available at convenience stores, add peanut butter to the banana or apple, and you've got a tasty treat.
8. Ready-to-eat protein: canned tuna or chicken, or even hardboiled eggs, are available in some convenience stores.
9. Chips and salsa. Many brands of tortilla or corn chips are gluten-free, and I recently found a bag of chips made from rice at a convenience store. It's not the healthiest way to go, but if you find baked chips it'll be a little better.
10. If you are really desperate, get a cup of coffee with LOTS of low-fat milk. If it's a self-serve place, think of it as having a little coffee with your milk. The protein and fat in the milk will sate your hunger until you can get a real meal.
So there! I hope these ideas will help the next time you find yourself stranded and in need of some gluten-free options in a pinch.