Unless you're dating David Blaine or some sort of Vegas-penis-ventriloquist you can't fake ejaculate. The proof is in the pudding. But the idea of fake orgasming is a different thing. Most women aren't necessarily going to spot check a condom for semen  after sex, or dig up tissues in the dark because their guy alleged to have orgasmed three minutes earlier. In other words, if it moans like a duck, then why wouldn't it ejaculate like a duck.  

But the real question is not "can he fake it" but "why would he fake it?". If a man is either too anxious, drunk or tired to ejaculate he might in fact opt for the fake-orgasm. He can simply vocalize the soundtrack to ejaculating and covertly pull out of your x, y, or z hole.  Then he must casually hide the evidence that there is no evidence of his "completion" by (A) quickly tying up the empty condom and tossing it or (B) if there is no condom, and lack of light permitting, pretend to ejaculate into a towel or tissue. Jizzing in the dark is easy, and, oddly enough a Josh Groban album if I'm not mistaken.
 
But what about no-condom-sex where the man "orgasms" inside? Good question, Here's the trick:

When the woman goes to pee or moves around and discovers there's zero semen leakage -  the guy says something cavalier and slightly insulting, like "I must have really shot it deep in ya." He then successfully turns the tables, spotlighting her "long and vacous vaginal cavity" not his own shortcoming. Its all parlor tricks: Slight of Hand, Slight of Vagina.

If a man can pull a rabbit out of his hat, be certain he can also pull a fake ejaculation out of his ass.