The court sentenced them to 2 months' imprisonment.

• They were sentenced to 2 months' imprisonment.
• They are sentenced to 2 months' imprisonment by the court.
• They were sentenced to 2 months' imprisonment by the court.

No one can accuse them of being unhelpful.

• They can't be accused of being unhelpful.
• They can't be accused of being unhelpful by no one.
• They aren't accused of being unhelpful.

They'll fire him when the truth is discovered.

• He'll be fired by them when the truth is discovered.
• He will fired when the truth is discovered.
• He'll be fired when the truth is discovered.

According to some sources, he was very ill.

• He is said/reported to have been very ill. / It is said that he was very ill.
• He is said to have been very ill.
• It is said by some sources that he was very ill.

The company is wasting so much money.

• So much money is being wasted by the company.
• So much money is wasted by the company.
• So much money is wasted.

The police have investigated the case.

• The case has been investigated.
• The case has been investigated by the police.
• The case is being investigated by the police.