The discount – which is capped at £10 per person and does not apply to alcohol – is available at more than 70,000 outlets across the UK throughout August.
It involves not only the major chains such as McDonalds, Nandos, and Starbucks, but also dozens of Michelin-starred restaurants.
Hungry diners can find out which local restaurants are taking part by entering their postcode on the government’s website.
The scheme runs every Monday, Tuesday and Wednesday between 3 and 31 August and can be used as many times as you like, and on top of other offers and discounts.
No vouchers are needed as the discount is automatically applied to the bill and the money is later reimbursed to the eateries by the government.
However the government has advised the public to follow guidelines if they are in areas under local lockdown and warns that restaurants may not be open even though they are registered in the scheme.
Many outlets taking part in the promotion are also encouraging customers to book ahead.
Those hoping to take advantage of the offer from midnight on 3 August may also be disappointed. One 24-hour bar contacted by The Independent said it was starting the scheme at 6am.
Announcing the scheme last month, Mr Sunak said that it is “vital” that the country sees “the hospitality industry back up and running”.
Among the chains taking part are All Bar One, Bella Italia, Browns, Burger King, Cafe Rouge, Castle pubs, Ember Inns, Frankie & Benny’s, Harvester, Las Iguanas, Miller & Carter, Nando’s, Nicholson’s, Oak Tree, Orchid Pubs. O’Neill’s. Pizza Hut, Premium Country Pubs. Pret A Manger, Prezzo, Sizzling Pubs, Starbucks. Stonehouse Pizza & Carvery, Toby Carvery, Vintage Inns, Wagamama and Wetherspoon’s.