And they'd get very hot in the sun so mint or something else that tolerates shade would be good.Never seen a special beer can . Photos?
Perhaps use them for cuttings or seeding, out of direct sunlight. Kitchen Cress? I have seen wine bottles cut off and they look stunning. The edges are ground flat for safety. You would need to turn the edges of the cans somehow or you risk slicing of your fingers. https://www.handmadecharlotte.com/diy-tin-can-herbs/https://www.instructables.com/id/Soda-can-seedling-container/http://www.swiish.com/blog-post/diy-tin-can-herb-garden/