score:11
Normally, you should not be asked for your passport on the Czech-German border. However, the situation in Europe is currently (spring 2016) not normal.
Due to the European migrant/refugee crisis, the Schengen travel area is under severe stress. Hundreds of thousands, perhaps millions of migrants/refugees are attempting to travel by whatever means possible from Turkey (or other countries) to northwestern Europe (Germany, Sweden, and other countries). In response, many countries have re-introduced border checks even on inner-Schengen countries.
Therefore, it is currently unwise to cross any border without a passport (or European identity card). Even if there may be no checks in one direction, there may be checks in the opposite direction. Even if there are no checks now, there may be checks next week. If that happens, you might get stuck on the Czech side of the border and be caught up in the migrant/refugee trail, which is probably not desirable.
Upvote:3
Since both countries belong to the Schengen Area, there is no regular passport control at the border, but there may be controls at random. Due to the recent refugee discussion those random controls have been increased.