When he started his crying fit, I told him to stop crying in a very calm tone. He refused to listen and kept on crying. I just sat there and waited for him to stop, occasionally, reminding him to stop before I will hug him. He sees no progress with me and thus look at my helper, giving those eye contact to ask her to carry him. My helper know better to interfere and thus, told him to stop and listen to mommy first.
He cried. He vomited. I still refused to give in. Can see that my helper felt the heartache too, so I brought him into my bedroom and let him continue his cry. He cried and vomited many times and finally realised that this crying doesn't work anymore and slowly, he stop. Once he stop, I gave him a big hug and explained to him that he cannot cry this way again. He nodded his head and I asked him to say "sorry" which he did.
Carry him out and washed him up while my helper cleaned up my room. She commented that the room look like a war zone with all the vomit patches everywhere.
After I changed him, reminded him again that he is not to cry this way again and whatever he wants, he has to ask properly. He nodded his head.
He did cry this way again after the "lesson" but whenever I said "stop crying" he stop immediately. Now, he didn't cried anymore, just normal soft whining like this.