When people talk about canned bread, they are almost always referring to B&M Brown Bread, the Maine-based company that is nationally renowned for its baked beans.
Its ingredients are very straightforward, and the flavor is really dominated by the marriage of molasses and rye, similar to the taste of pumpernickel bread.
Its texture has much more in common with a cake or muffin, and because it's leavened with baking soda rather than yeast, it is fairly dense with tiny air bubbles.
Many online reviews compare B&M's canned brown bread with bran muffins, in terms of both texture and taste. The subtle sweetness of the molasses gives it a bran-like flavor.
Admittedly, the idea of eating canned bread can be a hard sell to those who didn't grow up with it, and it doesn't help that the flavor is a bit of an acquired taste.