Survey by Save the Children indicates Afghan refugees returning from Pakistan are also vulnerable to forced labour.
At least 34 Afghan asylum seekers arrived in their home country after being deported from Germany a day earlier, a Kabul airport official said.
The group was the first to arrive back in Afghanistan after a new agreement was made between the German government and Kabul in October.
The Kabul airport chief of police, Mohammad Asif Jabarkhil, said the deportees, all young men without families, landed around 5am on Thursday.
Many expressed disappointment over their deportation, saying they had lived and worked in Germany for years and were now forced to come back without any job prospects.
Sidiq Kuchai, a 23-year-old from northern Baghlan province who was in Germany for seven years, said he “had a good job and was working in a restaurant in Cologne”, AP news agency reported.
Kuchai, who was among the returnees, said he had “no job and no security” in Afghanistan. He added: “I am not happy, everything is different for me here.”
Ali Hussaini, a returnee originally from central Oruzgan province, said he had little time to prepare and was told he was being deported by four police officers who came to his home.
“They came to my door at 4am in the morning, put handcuffs on me and threw me in a car,” he was quoted as saying by the DPA news agency.
Around one million refugees from Afghanistan, Syria, Iraq, parts of Africa and elsewhere have arrived in Germany since the beginning of 2015.
Anti-immigrant sentiment in the country has risen and groups such as the far-right Alternative for Germany (AfD) party have won support as they blame security and economic woes on refugees.
Interior Minister Thomas de Maiziere said in October that the group deportations were supposed to send a signal to Afghans that Germany only accepts a small number of asylum bids from their country.
The country has witnessed demonstrations against the deportations, saying much of Afghanistan is not safe for return.
More than 12,000 Afghans living in Germany, 5 percent of the Afghan population there, were due for deportation as of November, according to the German government.