UPDATE 1-Soccer-Inter hit six past Benevento at ghostly San Siro
Inter raced to a two-goal lead in less than 10 minutes against their Serie B opponents when Mauro Icardi converted a penalty and Candreva fired home the rebound after an Icardi header struck the post.
Dalbert blasted the third just before halftime in the round of 16 tie, the Brazilian's first goal for Inter since his move from Nice 18 months ago.
Argentine forward Martinez added two more in the second half and Candreva completed the scoring while Roberto Insigne and Filippo Bandinelli replied for the visitors.
There was a ghostly atmosphere at the huge San Siro as shouting from the players and coaching staff echoed around the arena.
"I didn't like it, it didn't feel like a real match," said Inter coach Luciano Spalletti.
"This is not sport or the kind of spectacle we want to see. If we talk about football being a spectacle, it is because of the fans who come to the stadium and enjoy themselves.
"We don't want to be in a stadium when it like this."
Earlier, two late goals from Federico Chiesa gave Fiorentina a 2-0 win at Torino.
(Reporting by Brian Homewood, editing by Ed Osmond)