It varies from person to person. For some, it can be painful and for others it can be completely peaceful.
There are also other factors you must consider like the urge to vomit and forcing yourself to avoid vomiting, which is very agonizing and I couldn't even prevent myself from vomiting for a very short time when I attempted and your throat burns after drinking the SN (at least that is what happened to me).
Different side effects include dizziness, feeling hot, tachycardia, etc.