Ten portable toilets and a bank of five taps were installed outside a centre run by the charity Secours Catholique a few kilometres (miles) from the centre of the northern port.
Between 450 and 700 migrants are thought to be sleeping rough in the region.
Local authorities said more sanitation facilities were planned at another location outside the town, which is the main launchpad for attempts to slip into Britain by truck across the Channel.
- French court rules government must supply water to migrants
- French court orders Calais to provide drinking water for migrants but not shelter
The interior ministry and the city of Calais had appealed against a June ruling by a court in nearby Lille to provide water and sanitation facilities for the migrants.
They said they feared that new makeshift camps would spring up like the notorious "Jungle", where up to 8,000 migrants lived in squalid conditions before it was demolished in October last year.
France's highest administrative court in late July rejected the appeal, saying the state's failure to provide for the migrants' basic needs "exposed them to inhuman and degrading treatment, dealing a serious and clearly illegal blow to a basic right."
Vincent De Coninck, an official with Secours Catholique, said the portable toilets and taps were far from adequate.
"It's less than minimal," he told AFP, adding that the authorities' "interpretation (of the order) is worrying. We hope it's just a first step, which is clearly inadequate."
The Lille court also demanded that those migrants who decide to seek asylum in France be offered a place in a reception centre wherever there is space available.
Two new centres opened in the region last month.
France's new centrist government has taken a tough line on Calais, with Interior Minister Gerard Collomb saying he does not want the city to become a "running sore."
President Emmanuel Macron has said he aims to find shelter for all those living rough in France by the end of the year.