What was on specific rule put in place by the east india company that angered and offended sepoys?

The East India Company forced Sepoys to use new ammunition that went against their religious beliefs, hence causing the Sepoy Rebellion.

It all started when the British East India Company implemented the use of new bullets that must be coated with a mixture of pork and beef fat. This upset many Sepoy's, as several of them were Hindus and this went against their beliefs. Hindus belief that the cow is a sacred animal and are prohibited from touching or killing cows and eating beef.

Along with this, many Sepoys were also Muslim. In this religion of Islam, the pig is considered an unclean animal. This upset with the new policies caused a revolt of these Sepoys against the British East India Company.