The 33-year-old then finished off a rapid counter-attack by shooting into the bottom corner after 65 minutes.
Embroiled in a heated discussion with Sassuolo's Federico Di Francesco, the Brazilian winger proceeded to spit into the mouth of Di Francesco before walking away.
Bolstered by five-time victor Ronaldo, Juventus begin their quest for the Champions League title which has eluded them in two decades in Valencia next Wednesday.
Just over 10 minutes after recording his first goal for the club, Ronaldo had his second.
"Today, even though it was the first time with this system, we did well".
"This was a game we had under control, we should have closed it down".
Coach Massimiliano Allegri had said before the match he was not concerned that Ronaldo has failed to find the net despite 23 shots at goal in the team's three wins out of three so far this season.
Inter Milan's woes were compounded with a shock 1-0 home defeat by Parma on Saturday ahead of their European opener against Tottenham at the San Siro.
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