it really does depend on facilities , time allowed for eating etc etc.
a tin of batchelors soup ( normally around 28-30 carb )
plus a couple of Jacobs cream crackers will be about 40 carb
alternatively , a sandwich made at home on wholemeal bread ( tuna mayo , egg , ham , beef )
plus an apple will be around the 40 carb mark
you could make a massive salad at home with lettuce , tomato , cucumber , spring onion , avocado , chunks of chicken ,steamed green beans , a few olives, green pepper , and an oil and vinegar dressing for around 12-18 carbs -- plus a slice of buttered wholemeal bread to make your approx. 40 carb