The world number four enjoyed a stunning season, finishing as runner-up at Roland Garros and Wimbledon, winning her second career title in Dubai and then triumphing with Italy in doubles at the Olympics and again in Malaga.
Sinner, who lost last year's final to Novak Djokovic, did not put a foot wrong this time round as he finished undefeated and without dropping a set to earn $4,881,500 in prize money.
Spanish superstar Rafael Nadal is aiming to cap his emotional farewell from tennis with another Davis Cup triumph in Malaga next week.
Fifth-ranked Fritz triumphed 6-3, 3-6, 7-6 (7/3) over world number two Zverev in a thrilling match at the season-ending event in Turin.
World number four Daniil Medvedev said the ATP Tour calendar needs to be refocused around the Grand Slams and Masters 1000 events with the lower-tier ATP 250 tournaments moved to an optional slot later in the year.
The small furry objects that are the focus of every tennis player's energy are spinning the stars at the ATP finals into a fury and leaving them deflated.
Czech Barbora Krejcikova on Sunday called for respect and professionalism in sports media as she hit out at "unprofessional" remarks made about her appearance during a broadcast on the Tennis Channel.
Nadal, the winner of 22 Grand Slam titles, announced last week that he will retire from tennis after the Davis Cup Finals in Malaga next month.
When a teenaged Rafa Nadal bounced in to Roland Garros in pirate pants and sleeveless shirt in May 2005 before scything through the draw, few realised it marked the start of an unprecedented era of sporting domination.
The 20-year-old's exit means Serena Williams remains the last woman to successfully defend the US Open title back in 2014.
Four-time French Open champion Swiatek was equally dominant as Sinner as the top-seeded Pole eased into the fourth round with a 6-4, 6-2 victory over Russia's Anastasia Pavlyuchenkova.
Djokovic, a four-time champion at the tournament and seeking a record 25th Grand Slam title, was leading 6-4, 6-4, 2-0 when Djere called it quits.
In the middle of the afternoon at Flushing Meadows, the searing heat reached 35 degrees Celsius (95 Fahrenheit).
Sinner marked his return to the courts for the first time since it was revealed he had failed two drugs tests, coming back from a set and break down to defeat Mackenzie McDonald at the US Open.
Midnight matches may be popular with fans but not with old campaigner Novak Djokovic, who bemoaned a late night at the start of his U.S. Open title defence on Monday.
Djokovic arrived on Arthur Ashe Stadium for his 40th career night match at the tournament with two gold bags slung over his shoulder in a nod to his recent Olympic success in Paris.
Gauff, seeded third, fired 10 aces and needed just 66 minutes to beat 66th-ranked Gracheva. She saved eight break points -- including two with aces in the final game
The US Open brings down the curtain on the 2024 Grand Slam season with newly minted Olympic gold medallist Novak Djokovic aiming to add to his cache of major titles after failing to do so since bagging No. 24 at Flushing Meadows last year.
Djokovic, who will once again bid for a record 25th Grand Slam title at Flushing Meadows, has been upstaged by younger rivals this season, losing to Jannik Sinner in the Australian Open semi-finals and Carlos Alcaraz in the Wimbledon final.