I highly recommend using black beans that you've cooked yourself (with a pressure cooker, or on the stove) in this recipe.
If you must use canned beans, you'll need to rinse them very well and omit the salt.
You may also want to start with ½ cup of beans instead of the full ¾ cup, as canned beans tend to have that super special "can" flavor.
If you don't like using bananas, you can use 2-3 dates or some maple syrup to sweeten this smoothie instead.
And of course, feel free to swap out the cocoa powder for cacao powder, or add a cup of spinach, a tablespoon of chia, and/or a sprinkling of cacao, if you're one of those people.
(Not that I could stop y'all from doing that by merely not mentioning it!)