The Nerazzurri never looked back after taking a seventh-minute lead through Rodrigo Palacio and were three goals to the good by half-time after Algerian midfielder Saphir Taider's effort and Raffaele Pucino's own goal.
Ricardo Alvarez got on the scoresheet at the beginning of the second half, while substitute Diego Milito added a brace either side of Esteban Cambiasso's fine strike to seal an impressive rout.
A successful outing at the Stadio Citta del Tricolore takes Inter to 10 points from their opening four league matches to give head coach Walter Mazzarri reason for cheer after arriving from Napoli this summer.
Sassuolo's problems continue to mount, however, with Sunday's mauling their fourth successive defeat in the league and they are firm favourites for a return to Serie B.
They nearly fell behind in the third minute as Fredy Guarin saw his long-range effort saved by Sassuolo goalkeeper Alberto Pomini.
However, the away fans would not have to wait long for the deadlock to be broken as Yuto Nagatomo's low cross from the left wing was easily converted by Palacio.
Jonathan Moreira narrowly missed the target from just outside the area before Inter doubled their lead after 23 minutes when Taider tapped in the rebound after Palacio's initial effort was parried by Pomini.
Sassuolo's luck showed no signs of improving as substitute defender Pucino accidentally headed into his own net from Taider's cross 10 minutes later.
To their credit, the Neroverdi refused to wave the white flag, although on-loan Genoa forward Antonio Floro Flores saw his effort from the edge of the area come back off a post.
Alvarez should have added Inter's fourth, but missed the target from close range, while at the other end Floro Flores failed to get on the end of Ezequiel Schelotto's right-wing cross that would have resulted in a certain goal.
Alvarez atoned for his earlier miss by scoring from the rebound in the 52nd minute after Palacio ended a flowing Inter counter-attack with a burst into the box and a shot which was parried by Pomini.
Still, the hosts had chances and Inter goalkeeper Samir Handanovic had to make a great save from Simone Zaza's header from point-blank range.
However, their deficiencies at the back were glaringly obvious as Milito notched the away side's fifth in the 64th minute after a tap-in following some good work from Alvarez.
Argentina midfielder Cambiasso curled magnificently in off the post with his weaker right foot from the edge of the box in the 75th minute.
Milito then completed the scoring eight minutes later with another easy finish after Guarin managed to work his way into the area before teeing up the 34-year-old Argentinian striker.