By Laura Smith-Spark
BBC News, Leipzig
Dutch fans are being handed orange shorts to watch the Argentina World Cup match if they wear trousers promoting a beer which is not the official sponsor.
Hundreds in the crowd were in their underpants for Friday's match
Up to 1,000 fans had to watch Friday's game against Ivory Coast in underpants after being denied entry because they were wearing the orange lederhosen.
Fifa said a bid at "ambush" marketing - free publicity at the expense of official sponsors - was not allowed.
But Dutch brewery Bavaria defended its decision to give away the lederhosen.
It said no sponsors had the right to tell fans what to wear.
American firm Anheuser Busch, maker of Budweiser beer, is among 15 companies to have paid up to $50m (£27m, 40m euros) each for the right to be an official partner at this World Cup.
Fifa spokesman Tom Houseman told the BBC News website that staff at the Ivory Coast match had been briefed in advance to look out for the trousers with Bavaria slogans and logo.
Officials were instructed not to ask fans to remove the lederhosen if they had only underwear underneath, he said.
"The idea of hundreds of fans removing their trousers is always potentially amusing, and our suspicion is that trousers were chosen as an ambush tool specifically because of the publicity that fans taking them off would generate," he said.
"As a goodwill gesture this evening, I have provided gate staff tonight with piles of spare pairs of plain orange shorts should anybody require them."
Mr Houseman added that individual fans wearing items not made by the official World Cup sponsors need not worry about being turned away.
Bavaria has defended its decision to give away the orange lederhosen with purchases of its beer.
"I understand that Fifa has sponsors but you cannot tell people to strip off their lederhosen and force them to watch a game in their underpants," Bavaria chairman Peer Swinkels told Reuters news agency.
"That is going too far."