I don't recall Daniel Larusso saying that. What part of the movie was that in?
It was in the straight-to-video and little known release Karate Kid 4: Sweep the Net.
In that movie, Mr. Miyagi has his identity stolen by a Nigerian hacker dojo. He enlists Daniel and one of Daniel's friends, an overweight hispanic kid who provides comic relief, to help him track down the hackers. Once the hackers are discovered, they challenge Miyagi and the two kids to a karate duel. If Miyagi's kids win, the hackers will shut down their operation. The day before the match, Daniel comes down with appendicitis and the chubby hispanic kid has to sub for him. He implements the "brush your teeth" move that Miyagi teaches him and defeats the Nigerian hackers.
When Miyagi and the porky hispanic visit Daniel in the hospital after the duel, Daniel asks what happened to the hacker's operation and the portly hispanic cracks "We forgot to pay the hosting bill." Everyone laughs and the credits roll with "I'll Tumble For Ya" by Culture Club playing over the credits.