However, Brazilian teenager Joao Fonseca's first Grand Slam campaign came to an end in the second round.
Another teenager did make it to the third round, though. American qualifier Learner Tien created the biggest upset so far as he stunned Russian fifth seed Danil Medvedev in a near five-hour epic that finished close to 3am.
Major champions Iga Swiatek, Emma Raducanu and Elena Rybakina progressed as bright Melbourne sunshine replaced Wednesday's rain and Sinner's compatriot, fourth seed Jasmine Paolini, joined them in the cool of the evening.
There was nothing cool about 10th seed Danielle Collins's 7-6(4) 4-6 6-2 victory over 195th-ranked Australian Destanee Aiava. The American blew kisses at the booing fans on Kia Arena and thanked them for paying for her next five-star vacation.
"One of the greatest things about being a professional athlete is the people that don't like you and the people that hate you, they actually pay your bills," she said in a lively press conference.
Even the preternaturally chilled Sinner looked ruffled after giving up his first set in 14 matches in the first evening match on Rod Laver Arena, where local wildcard Tristan Schoolkate rose to the occasion with some fine early tennis.
The world number one converted his first breakpoint midway through the second set, however, and was soon back in his groove and romping his way to a 4-6 6-4 6-1 6-3 victory.
"He was playing some great tennis," Sinner said. "It was a tough match to get through. I'm happy with how I handled the situation. Obviously I can improve for the next matches, but I'm happy that I'm through."
Fonseca's stunning demolition of ninth seed Andrey Rublev on his Grand Slam debut on Tuesday meant fans were queuing around the block for his second-round match against Italian Lorenzo Sonego. They got their money's worth with a five-set thriller even if 18-year-old Fonseca ended up on the wrong side of a 6-7(6) 6-3 6-1 3-6 6-3 scoreline.
"I need to have more experience on this," said Fonseca. "I need to work more to stay mentally focused during the whole match and need to be prepared for this."
Fonseca is part of another generation of rising stars and 19-year-old Tien can definitely be put in that category now, after outlasting Medvedev 6-3 7-6(4) 6-7(8) 1-6 7-6(7) to become the youngest American man to reach the third round since Pete Sampras did so aged 18 in 1990.
But he gathered himself for an epic fifth set, winning six of the last seven points in the deciding breaker to extend his Australian Open debut.
"I'm just pretty happy to be off the court. I don't think I've played a match that long ever, or even spent that much time on a tennis court straight," Tien said.
MEDICAL TIMEOUT
Five-times Grand Slam champion Swiatek earlier shot out of the blocks at the start of the day on Rod Laver Arena to crush Rebecca Sramkova 6-0 6-2 and set up a clash with Raducanu.
"I felt pretty confident, and I started the match well so I just kept going," said Swiatek. "It was good to play in such an efficient way and just finish it quick."
Former Wimbledon champion Rybakina overcame a second-set wobble to beat 17-year-old American wildcard Iva Jovic 6-0 6-3, the second teenager she has sent packing from the tournament.
Raducanu, who has struggled with injuries since her 2021 US Open triumph, required a medical timeout for a left hip issue at 0-3 in the second set against Amanda Anisimova before seeing off the American 6-3 7-5.
Paolini wasted no time getting through her evening match against Mexico's Renata Zarazua, winning 6-2 6-3.
US Open champion Sinner will next face Marcos Giron, one of six Americans who made it into the third round and are looking to end their country's 22-year wait for a men's Melbourne Park champion.
Fourth seed Taylor Fritz romped past qualifier Cristian Garin 6-2 6-1 6-0 and Ben Shelton took out Pablo Carreno Busta 6-3 6-3 6-7(4) 6-4.
Alex Michelsen soon joined them with a 7-5 6-3 7-6(4) win over Australian wildcard James McCabe and Giron prevailed 7-5 3-6 7-5 3-6 6-4 over Argentine Tomas Etcheverry to make it five.
Frances Tiafoe, the 17th seed, was unable to maintain the American charge, however, and he went down 6-7(3) 6-4 3-6 6-4 6-1 to Hungary's Fabian Marozsan.
Holger Rune's tie against Italian Matteo Berrettini on John Cain Arena had five-sets written all over it but the Danish 13th seed finished it in four 7-6(3) 2-6 6-3 7-6(6).
