The women were part of a group of 12 who were arrested in June after leaving El Izba Baptist Church in the Sudanese capital, Khartoum.
They were accused of public indecency and are thought to be between the ages of 18 and 23.
According to Christian anti-persecution charity Christian Solidarity Worldwide (CSW), the women, who were wearing skirts and trousers, were taken to a police station and forced to remove their clothes, which were submitted as evidence to the prosecutor.
Two of the 12 were released without charge whilst four others were released without charge. One is still awaiting trial.
The remaining five women, Ferdoos Eltoum, Rehab Omer Kakoum, Nasra Omer Kakoum, Wegdan Aba Alla Salih and Uthan Omer Eljaily, were convicted and fined 500 Sudanese pounds, which was later reduced to 50 Sudanese pounds (approximately £5).
The anti-persecution charity Christian Solidarity Worldwide is concerned that the authorities have a broad scope to define what constitutes indecent or immoral dress.
It said the increase in cases being brought against individual Christians seems to be part of an on-going campaign of repression against religious minorities in Sudan.
Sudan is a Muslim-majority country, with just over 1 in 4 people being a Christian.
CSW Chief Executive, Mervyn Thomas said: "While we welcome the fact that four of these women were found innocent, we question how some have been found guilty when they were all dressed similarly and entirely in keeping with the law and Sudanese customs.
"We are deeply concerned by the arbitrary application of the law and the exploitation of its ambiguity to deliberately target these innocent women.
"These cases highlight wider concerns regarding the mistreatment of religious and ethnic minorities in Sudan.
"We urge the authorities to respect the right to freedom of religion or belief, as defined in Article 18 of the International Covenant on Civil and Political Rights (ICCPR), to which Sudan is party, and to review or repeal article 152, since its lack of definition facilitates subjective arrests and random judicial decisions."
