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?