Which costs are reimbursed when travelling with Deutsche Bahn?

Only second class trips are reimbursed. Also, if you are employed by the FU, you have to use their corporate discount. However, the discount is only applicable for trips with the “Normalpreis”, not trips on “Sparpreis” or those where you use your private BahnCard.

Also, be aware that potential markups on tickets bought at ticket machines cannot be reimbursed, unless you can show the necessity.