The police have launched an investigation after unknown persons poured butyric acid into the away block of Heidenheim's stadium before their Bundesliga match against RB Leipzig, a spokesperson told dpa on Sunday.
Butyric acid has a very unpleasant odour and several Leipzig fans complained on social media about the smell in the visitor's area before the kick-off.
A spokesperson for Heidenheim said that the affected area was cleaned, but the bad smell remained during the match.
Heidenheim coach Frank Schmidt condemned the action in the strongest possible terms.
"I lack any form of understanding. Anyone is entitled to an opinion - even about RB Leipzig. But doing something like that? I'm ashamed of it. That's not right," he said and apologized on behalf of the club.
Leipzig and their fans have been criticized for years due to the club's links to energy drink company Red Bull, which is seen as a threat to the traditional 50+1 rule in German football.
The rule means that clubs cannot be majority owned by one investor, but Bayer Leverkusen (owned by Bayer Pharmaceuticals) and VfL Wolfsburg (owned by Volkswagen) have exemptions.
Leipzig say they are not directly owned by Red Bull, but they still have a complicated ownership structure which does not breach the rule.