Rev Hassan Abduraheem and Rev Kuwa Shamal have also asked to be transferred to a formal prison facility where their basic needs can be met.
Rev Abduraheem has been held in the attorney general's custody since early May and Rev Shamal has been detained since the end of May.
The men are being investigated for national security crimes and have not been formally charged.
In June, their lawyers requested that they be released on bail until they are formally charged but this was denied due to the seriousness of the potential charges.
The pair spoke out about their living conditions and personal safety at the end of July.
At present, they are living in police holding cells which are usually used to keep suspected criminals for short periods of time while the prosecutor investigates potential criminal charges.
Christian Solidarity Worldwide (CSW) has been told the men "are held in a small room where sometimes up to 25 men are also detained.
"Their diet is poor and their health has suffered."
At the end of July, Rev Shamal (pictured) contracted malaria and his legal team requested medical attention, however, it has been reported that he was only treated after his church found the money to pay for it.
Doctors also discovered he was suffering from a blood infection caused by poor diet.
Both men were originally arrested in December 2015 and have been arrested since.
Reports from Sudan suggest that confiscations and demolitions of churches have increased since South Sudan's independence in 2011.
CSW's Chief Executive Mervyn Thomas said: "We are deeply concerned to learn of the unsanitary and unsafe conditions in which Reverends Hassan Abduraheem and Kuwa Shamal are being held.
"We echo their request for the prosecutor to either submit their case to court or release them immediately and unconditionally. Their prolonged detention in police custody is highly irregular and falls short of the reasonable time frame articulated in article 9 of the International Covenant on Civil and Political Rights, to which Sudan is a party.
"We are also alarmed by the decision to confiscate church buildings belonging to the Episcopal Church and the Sudan Church of Christ.
"We urge the government to reverse this decision, in accordance with constitutional guarantees of the right to freedom of religion or belief, which includes ownership and access to places of worship."
