Final answer:
Bhai Gulab Singh disguised himself as Banda Singh Bahadur, allowing Bahadur to escape the fort of Lohgarh and sacrificed his own life in the process on December 10, 1710.
Step-by-step explanation:
The Sikh who sacrificed his life by disguising himself in the garments of Banda Singh Bahadur to allow Bahadur to escape from the fort of Lohgarh was Bhai Gulab Singh on December 10, 1710. Banda Singh Bahadur was an eminent Sikh warrior and a disciple of Guru Gobind Singh, who fought against the Mughal empire's oppression. This act of sacrifice by Bhai Gulab Singh is remembered as an event showcasing the courage and loyalty of the Sikhs during a time of persecution and hardship.