Derby Crown Court heard an onlooker filmed Reece Mackender and Martin Hopkinson as they abused the girl and “no-one tried to intervene”.
Eventually, after the youngster’s ordeal was over and she sat crying on a bench, the pair were chased off by a member of the public.
Police were called and Mackender was found “hiding behind a shower curtain” at an address he was traced to by police.
Judge Jonathan Bennett told Mackender, 29, and Hopkinson, 36: “This was a Saturday afternoon in a popular park – there were a lot of people around, children and families.
"It was a lovely day, a bit like today – it’s in that context that this quite shocking offence took place.”
James Bide-Thomas, prosecuting, told how on the day of the offence after spotting two young girls at Somersall Park the defendants waved the two girls over.
He said: “They both started speaking to them and and gave them cider – they started asking them sexualised questions.
"Both girls started to feel drunk and the defendants persuaded them to go to a supermarket to shoplift alcohol.”
After the girls returned with bottles of Smirnoff Ice and Disaronno one of them became scared, called her boyfriend and left the other alone with the two defendants.
Mr Bide-Thomas said: “She recalls someone pulling her along the ground by her ankles, which left scarring on her back.
"Martin Hopkinson then pulled her towards him by her legs, pulled her underwear to one side.”
“Several members of the public could see what was going on but no-one intervened – one member of the public filmed part of the incident and put it on Snapchat,” said Mr Bide-Thomas.
After police were called to the scene at around 6.15pm both girls appeared “drunk” and were “distressed and crying”, the court heard.
The court heard the young girl who the two men had sex with was later found to have a blood alcohol level of 98 micrograms in 100 millilitres of blood.
Judge Jonathan Bennett noted that she “had not really tasted alcohol before, apart from the occasional glass of wine”.
Both girls, said Judge Bennett, had planned to spend the night at a sleepover at one of the girl’s houses.
The worst-affected girl had been forced to move school due to the Snapchat video and had been left with scarring still on her back which others often asked her about, the court heard.
Gregor Purcell, for Mackender, said his client has undertaken victim awareness course since he has been remanded into custody.
He said: "This is a defendant who does not bear any prior convictions for offences of this kind. When he is released he will move away from Chesterfield."
William Bennett, for Hopkinson, said at the time his client was taking cocaine and drinking alcohol.
He said: "It should not have happened, it did, he is full of shame for his actions."
Hopkinson, of Chester Street, Chesterfield, admitted sexual activity with a child, possession of indecent images of children and an extreme pornographic image.
He was jailed for five years and none months.
Mackender, of Stone Row, Chesterfield, was found guilty after a trial of sexual activity with a child. He was jailed for eight years and ordered to serve at least two-thirds of the sentence.
Both men were made subject of sexual harm prevention orders.