Nah to be on the safe side I would say the "guarantee" is with antiemetic and following the guide to the letter. I don't know if there is one without, but for the reasons above, its possible.
I don't believe anyone has ever posted on here they took the second drink and survived. But they also follow the guide. I was in conversation with one person off-site who vomited then prepared and took 2nd shot almost immediately after and they apparently ctb.
Yeah this is what I don't get why people worry too much about the taste of SN or the discomfort. I mean maybe if you think you can't get the drink down.
It's 20 minutes of mild discomfort compared to all the potential suffering if you continue living.
One of the main reasons I haven't ctb yet is the finality of it, if I could get over that then taking SN is not worse than what I go through everyday anyway.