low or no carb foods are great for snacks if you don't want that extra injection to cover a snack. My daughter often snacks on low or no carb foods. Here are some examples:
sugar free jelly
eggs
cold meats (chicken drumsticks, ham)
cheese
celery, cucumber, carrot sticks with a dip like gucamole
avocados
mushrooms
salads with meat (ham, chicken, bacon), eggs or fish (tuna)
tomatoes
These following snacks are low in carbs but not carb free. sometimes you can get away with a low carb snack without an injection but you'll need to test to find out:
berries (strawberries, blueberries, raspberries)
melon
popcorn
natural yoghurt