A basic claim to get food for free or at reduced prices does not exist in Germany.
If you are entitled to unemployment benefit II or to social assistance, you can receive help for your livelihood if you cannot adequately cover your need for food, shelter, clothing, household effects, etc. For the conditions for claiming a living allowance, please contact the Employment Agencies or the responsible social welfare offices in the federal states. Employment agencies close to where you live can be found at www.arbeitsagentur.de/privatpersonen. The responsible social welfare office can be found at http://www.sozialaemter.com/.
If you are entitled to social benefits, you have the option of receiving groceries for your daily needs from the “Tafeln”: http://www.tafel-hessen.de/index.php?id=22
Bremer Tafel e.V.
Brauerstr. 13
28309 Bremen
Church facilities help as well, if you need help.