Food and drink
Germany doesn't have a great reputation worldwide for the quality or uniqueness of its food. The only even remotely famous foods are sausages (or wurste), schntizel, and sauerkraut. While all of these are delicious and widely available in Germany, they do very little justice to the quality and variety of food available here. In Germany as in the UK, the immigrant population has brought with it a wide range of restuarants and takeout food from diverse ethnic origins. Whether you want Italian, Turkish, North-African or East Asian foods, you will find it somewhere in Germany. And if that's not enough I guess you can always go to McDonalds.
Self-catering
Germany is the home of the discount supermarket, and there are certainly branches of Lidl and Aldi on every street corner in many cities. These are perfect for picking up supplies if you are cooking in a hostel, or have a kitchen to prepare lunches for a week, but if you just looking for lunch for one which can be prepared on the road you might find you are better off in an ordinary supermarket or delicatessen. Take advantage of your location to try some of the more interesting foods eaten in Germany. Even the cheaper stores are likely to have tubs of Herring, pickled and served in cream sauce, and jars of pickles. Also try a range of different sausages. Whilst some of the more revered and famous types taste little better than the cheapest hot-dog weiners, there is a huge variety and at least one for every taste.
Beware of deposits on bottles and drink containers of all kinds in Germany. The word for depost is pfand, and the amount you will have to pay is normally listed next to the price of the product on the shelf. Ideally you should just use the contents and take the container back for recycling like a good citizen - you will then get your deposit back and everybody will be happy. If you are leaving the country however, or just can't be bothered to deal with an added transaction in a strange language, you can avoid paying deposits for most things by buying them in tetra-pak style cardboard cartons.