Breadsticks, crackers, mini pitta breads with hummus to dip in, dry cereal (shredded/Cheerios), a brioche roll (Aldi), flapjack, shortbread, finger sandwiches (usually just cheese or cucumber)
Cucumber slices, carrot batons, banana, strawberries, blueberries, mini peppers or pepper slices, raisens, small apple, satsuma,
Cubes of cheese in a pot with sliced apple
Yogurt tubes
If it's really cold, a flask of vegetable soup or beans with a bread roll