If someone is sharing fake news, there are several punishments they may face depending on the nature of the crime. Many laws have punishments for fake news. Some of them are:
Publishing or circulating any statement, rumour or report
Section 505(1) of Indian Penal Code, 1860 has a punishment for making, publishing or circulating any statement, rumour or report which may cause fear or alarm to the public. The punishment is jail time of up to 3 years and/or a fine.
Section 54 of the Disaster Management Act, 2005 discusses the punishment for making or circulating a false alarm or warning as to disaster or its severity or magnitude, leading to panic which is jail time of up to 1 year or a fine.