Heat the olive oil in a pan over medium-high heat. When hot add in the onions and garlic and sauté for about 5 minutes until the onions turn translucent and begin to brown. Add the black beans, BBQ sauce, and salt and pepper to taste. Heat through.
Pile the beans on bread, toast, or a tortilla, garnish with cilantro, then drizzle a little extra BBQ sauce on top.
BBQ Black beans can be prepared ahead of time. If bringing to work, I like to bring them in a separate container, so I can heat them up before piling them on the bread, If that seems too fussy, this sandwich is still great cold too!