Four puppies were rescued by border guards after cruel owners left them in a box with no air holes.
The little pooches were found "gasping for air" by officials, who investigated after hearing strange noises coming from the unmarked box during a routine stop.
The discovery was made at the Moillesulaz border between Switzerland and France, a short distance south-east of Geneva.
Border guards say they stopped a car for a check and saw the cardboard box on the back seat.
They heard gasping noises coming from it and looked inside to see the dogs "completely dehydrated and lying in their own excrement."
Two other dogs were also found in the boot of the car, which officials say had been driven all the way to Switzerland from Portugal by the two unnamed Portuguese nationals.
The four neglected puppies were taken into care, and are now in an animal shelter being nursed back to health. It is expected they will be found new homes once they are back to full health.
Spokesman Michel Bachar of the Geneva Border Corps said: "What is especially shocking is that they have been travelling for 24 hours."
He added that a vet was called to the scene after the Portuguese owners confessed that the pooches were not fully vaccinated.
In order to be able to bring a dog into Switzerland, they must be vaccinated against rabies at least 21 days before arrival. Three puppies had only been vaccinated the week before and one not at all.
The four neglected dogs are now in a shelter in the town of Collex-Bossy, and are "doing well" according to animal shelter bosses.
Police confirmed a case of animal cruelty had been opened against the two owners who also had their car confiscated as they could not pay a 1,500-CHF (1,230-GBP) fine.
Bachar added: "Unfortunately these kinds of cases happen a dozen times a year, we are very attentive to this problem."
The two owners were not named in reports.