Additional meal allowances are flat-rate reimbursements of additional expenses for food and drink incurred on business trips at home and abroad. These additional expenses can be claimed as deductions on the basis of the (international) per diems specified in the German Income Tax Act (§ 4 (5) Sentence 1, Point 5 EStG in conjunction with § 9 (4a) EStG).
Source: Wikipedia, edited (only available in German)