Coppell told the club's website: "Helsingborgs are a good team and they took advantage of our deficiencies.
"We've been concentrating on trying to play a certain way and we were caught out tonight."
Coppell admitted that the game had been too one-sided, but added: "It was always going to be a learning curve for us.
"I think all the goals came from us losing possession in our own half. We were found out by a very good team.
"I thought we would cope better than we did but it's better that it's done now. We can learn from it rather than having it happen during the course of the season."
City, who drew their first tour match 1-1 with IFK Gothenburg, face Vallens in the third and final game on Saturday.
Bristol City (v Halsingborgs): Gerken, Edwards (Orr 55), Cisse, Fontaine (Nyatanga 55), McAllister (Ball 66), Jackson (Sproule 55), Elliott, Skuse (Johnson 55), Akinde (Clarkson 55), O'Flynn (Adomah 55), Campbell-Ryce.
Source: BBC Sport
Source: BBC Sport