Factual error: The ambulance Major Teppel transports the prisoners in is a Dodge WC54, which is an American military ambulance, not a German one.
Factual error: Hogan and his men are in Berlin to capture a traitor. They arrive at the Hotel Berlin in an ambulance and park near a K2 phone booth, something only found in England and its colonies, certainly never in the heart of Nazi Germany. (00:13:55)
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.