How to express sarcasm?
Intonation works, but particles and certain rhetorical phrases can also reveal mood:


哎，那部电影岂能没有意思呢。


果然 is often used sarcastically, to indicate an unexpected outcome:


在淘宝上订购了一条USB电缆，果然收到了指甲油为礼物。


Often the context is self-evident, just like in other languages:


对啦，真真想吃下那四天前做的谄媚的面条。