UK slang: "I've got nothing." or "Nothing came of it."
I think it comes from something like 'couldn't even get a drink at the pub, just left with some stolen mustard pacs'.
Did you get the (job/girl/money/news)?... Nah; "pocketful of mustard."
A pocket full of drugs of some type, typically weed, or some other type, since hippies associate themselves with the sun for some reason.
"Hey Bob, that football captain guy is sooo hot that I get a pocketful of sunshine when I see him."
"what? You get a pocketful of drugs from him?"
"No, he just makes me sooo hot..."
"Where'd you get that definition? From that first definition of pocketful of sunshine that retard made?
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi