Back when I was a provider almost 30 years ago, the focus of my all of my sessions was getting the client off. And, because ejaculation is an autonomic nervous system response, I would never offer or promise to be able to do so as part of interactive activities. I did have one client with that requirement, though unspoken, but all he wanted to do was jack off next to each other, which was entirely achievable.
Now that I'm a client, based on my past experience, I never expect it. I do always ask a provider if they want to get off after or with me, and am gratified when they do.
All of that said, if someone agreed to and couldn't, they really shouldn't try and fake it somehow with other liquid substances. Reminds me of the joke:
Q: How does a gay man fake an orgasm?
A: He spits on your back.