Hello. Just wanted to ask is someone here have experience sponsoring a spouse who is currently undocumented in the USA. I am a Canadian Citizen and I would like him to sponsor him.
It's certainly doable. You will follow the normal spousal sponsorship process using the outland route.
Your spouse will need to be 100% honest about his status and immigration history in the spousal sponsorship application.
There is always some chance your spouse might have to appear at an interview. If that happens, it will be held in your spouse's home country. You should aim to put together a strong application with solid proof of your relationship to avoid an interview.
Note that if he's been in the US without status for more than 1 year, he will be automatically banned from the US for 10 years once he leaves. This means that once he becomes a Canadian PR and comes to Canada, he will not be able to return to the US for 10 years. Make sure he's aware of this in case he has any immediately family members there.