He personally paid for his family members' flights and meals and used company funds for his own flights, accommodation and food.
On the last night of the trip, Sherry offered his young son a slice of pizza that was left over from his own A$32.50 order that was paid for by the company card.
The Australian reports Sherry was later questioned about his spending by Toyota bosses, and he told them his son had eaten part of his meal.
Citing documents lodged in the District Court of NSW, the publication revealed Toyota claimed Sherry had broken company rules by purchasing the "meal for his son".
It also accused him of booking a bigger hotel room than necessary and staying an extra night for "personal" reasons, although Sherry argues prices were higher as the trip coincided with the Australian Open, and he stayed the final night as he believed he would miss Sydney Airport's cut-off curfew.
Sherry is now seeking A$301,000 ($313,000) in damages.
A Toyota spokeswoman told news.com.au that "Toyota Australia takes compliance with our code of ethics, and associated policies and procedures, very seriously" but the company "won't be commenting on the matter further".
While Sherry's case has landed in the District Court of NSW, lawyer Alexandra Targett, from McDonald Murholme Solicitors, told news.com.au that unfair dismissal cases were generally filed in the Fair Work Commission.
She had some words of advice for fellow Aussies who may believe they have been treated unjustly at work.
"An unfair dismissal refers broadly to a dismissal that is harsh, unjust or unreasonable. The Fair Work Commission takes a range of factors into account when determining whether a dismissal is 'unfair' – such as whether there was a valid reason for the dismissal and whether the procedure followed was fair," she said.
"If an employee breaches a company policy or procedure relating to the company credit card, this may give rise to a valid reason for dismissal. However, the Fair Work Commission might still determine that the dismissal was harsh or disproportionate to the conduct alleged.
"For instance, if the breach was minor or substantial mitigating factors were disregarded, the dismissal might be found to be 'harsh' and therefore 'unfair'."
She said if someone believed they had been unfairly dismissed, they had a few legal avenues available.
"The primary two legal avenues are an 'unfair dismissal' claim or a 'general protections' claim. There are key differences between these two types of claims," she said.
"An unfair dismissal claim focuses on whether the dismissal was harsh, unjust or unreasonable, whereas a 'general protections' claim focuses on whether there was an unlawful reason for the dismissal.
"The purpose of general protections laws are to protect workplace rights, freedom of association and provide protection from workplace discrimination (such as) for age, gender or nationality."
