'Sti cazzi, is often used ironically to express and exhibit lack of interest in something, like "I don't give a ****" in English ("Abbiamo perso pure stavolta, eh? E sti cazzi!" = "So we lose again, huh? Well, I don't give a ****!"), or like a violent negation (Se ti presto la macchina? Sti cazzi! - What about I lend you my car? Absolutely No!)
source /wikipedia