Use for a different purpose: section 153b StGB comes into consideration, not fraud.
Anyone who uses a lawfully granted subsidy for a purpose other than the one approved falls under the misuse of a subsidy under section 153b StGB. What is decisive is that the subsidy was first awarded rightfully and is only afterwards used for a different purpose. From a legal perspective this distinction is central, because it decides on the applicable offence and the penalty range.
The amount of the subsidy concerned is important, because the penalty range is graduated. An early legal examination clarifies whether a use for a different purpose exists at all and what consequences are looming.