There are cases of people who have drunk only SN and probably succeeded.
Even a few grams of SN can be fatal, so for this reason, anyone should not test SN if they do not want to die.
Antiemetics are highly recommended, but they are not completely necessary.
It is very important in the whole process not to vomit, or to vomit as late as possible. Antiemetics are to help with this.
The more and faster SN is absorbed by the body, the better.
However, even taking antiemetics does not guarantee that the person will not vomit. It is a bit of a lottery.
Also, if the person vomit, it does not automatically mean failure.
Such a person can still die.
So it is possible to succeed without antiemetics, but CTB can be less pleasant and the probability of success decreases.
It is hard for me to say how much the chance of success is lower.
You definitely have to mentally prepare yourself for vomiting.
It is better to prepare for the worst-case scenario.
Fasting and a few glasses of SN increase the margin of error.
Make your own responsible decision.
Good luck.