From the whole conversation, I think the meaning here is "crazy" (though the handlebar moustache was a nice touch). ;) You might describe a crazy person as a "fruitcake" - there's a clever simile we use: "as nutty as a fruitcake". "Nutty" can also mean crazy, as well as the literal meaning of "nut flavour" or "lots of nuts". I wonder if the sense of "crazy" evolved into the meaning in GTA.

Thank you, I have discovered a new cool dictionary, but I think there's definitely perverse subtext here ;)

For this kind of slang, I suggest you use the website "Urban Dictionary". Use it with some care, as the definitions are not always correct! For the term "fruity", I think the second definition is fairly accurate: https://www.urbandictionary.com/define.php?term=fruity It is also in Merriam-Webster, the dictionary. There it is defined as "slang :crazy, silly".