The incident occurred last December outside the Royal Palace, the official residence of the Swedish monarch.
The soldiers, aged 25-27, were celebrating their final shift and had asked permission for a few hours' leave before their shift began at 10pm, reported the Sydsvenskan newspaper.
They went out in Stockholm's Old Town (Gamla Stan), visiting local bars, and heading back to the castle several times asking for extended leave.
It wasn't until 11pm when passersby noticed them smoking and chatting amongst themselves, which is not allowed when on duty.
The officer in command confronted the soldiers, who were carrying loaded AK-5C assault rifles with bayonets, and noticed how intoxicated they were. They were then taken to a police station and had their weapons confiscated.
There, the soldiers admitted to have been drinking but were too drunk for interrogation.
An alcohol test was carried out at 2am, four hours after they had stopped drinking. The result showed that they had a blood alcohol content of 0.6, 0.75, and 1.59 promille respectively. By comparison, the limit for drunk driving in Sweden is 0.2 promille and 1.0 promille for aggravated drunk driving.
The soldiers were charged on Friday with misconduct and risk fines or up to two years in prison.