There are a number of foods, like soda crackers, that expand a bit in the stomach.

Injera is an interesting flatbread, because it is fermented it rises a lot and is spongy on the inside, like a really light pancake. The teff flavor pairs well with the spiced meats and vegetables that are a large part of Ethiopian cooking.

I've seen recipes for it that use a basic sourdough starter, that's on my list for a summer meal.