In the sitcom, Two and a Half Men, Charlie composes jingles for actual products, like cereal, Pepsi etc. And even sometimes for shows on TV like Oshikuru. Some of them are really catchy and you get a sense it should be used in the real world. Were his jingles made by someone else in the real world and used on products, and later adopted in the sitcom or was it made just for use in the sitcom and not in the real world?
I'm going to say they're fake and created for the show.
IMDB Trivia states:
Charlie Sheen does not play the piano on the show. He is dubbed by composer Grant Geissman, who plays offstage while Sheen fakes it on a dead keyboard. With composer Dennis C. Brown, Geissman also writes the music for the jingles Sheen's character creates.
However, as with a lot of their trivia, it doesn't actually cite any sources to back this up.
The musicians for the show, as stated above, are:
Series Music by
Dennis C. Brown ... (234 episodes, 2003-2014)
Grant Geissman ... (234 episodes, 2003-2014)
It's well known that Geissman, along with Lorre, composed the theme song for the show. I would argue it stands to reason that Geissman, along with the other musician, composes the jingles for the show.
I would base this on a few things, including: a) the jingles not appearing to exist anywhere other than in the show, and b) the jingles are just a standard part of the music of the show and thus udner the domains of its two musicians.