You can even die if you drink too much water.
But in the case of CTB, what matters is the probability of success and perhaps comfort.
You would have to drink relatively a lot of Sodium Nitrate.
I don't know how many exactly.
Certainly much more than the SN.
Potential CTB may be more painful.
Also the probability of success is lower.
You're more likely to vomit than drink enough sodium nitrate to die.
This is also a little-researched method.
Overall not worth it.
Sodium nitrate IS NOT a replacement for SN.
If you can't get SN, don't try CTB with sodium nitrate.
There is simply less chance of success.
It's better not to mess around in such matters.