You don’t need an ID in Germany to vote just, push comes to shove, a way to make your identity believable. Expired ID, student ID, personalised public transport ticket, perfectly sufficient. Generally you just vote with your election notification, a sheet of paper with your address, ballot location, and number in the voter registry on it. If you try to vote with an ID but without notification workers are going to roll their eyes because they’ll have to manually search for you in their lists, heck, you might’ve turned up at the wrong location.