The Indian batsman was appointed UNICEF's ambassador for South Asia, helping promote sanitation in a country where more than half of the 1.2 billion population defecate in the open.
Tendulkar told a packed press conference it was a "second innings for him", adding: "This innings is important and dear to me, so I will do my best here."
Karin Hulshof, regional director of UNICEF, the UN children's fund, said 681 million people lack toilets in South Asia.
In India, 53 percent of the population or about 640 million people lack toilets and defecate in the open, the country's 2011 census data showed.
"Another statistic which baffles me and I was disheartened to know that 1,600 children die everyday worldwide because of diarrhoeal infected diseases," Tendulkar said.
Recounting childhood memories, Tendulkar said: "I would play cricket downstairs with my friends, with a tennis ball, and occasionally did not bother washing my hands and (would) want to eat after coming back home."
"My mother made sure that I washed my hands properly and ate with clean hands,? he said, stressing the need for personal hygiene.
Tendulkar, the world's leading scorer in both Test and one-day cricket, made a tearful final departure from the sport earlier this month after his 200th Test match, ending a glittering career spanning 24 years.
Tendulkar, a member of parliament, has been involved in several social causes in India relating to health care and education.
He has endorsed everything from BMW cars to energy drinks and biscuits to travel portals, but has not promoted tobacco and liquor-related products.
Tendulkar has yet to disclose his professional plans post-retirement.