You can cash a check for a stranger if they endorse the check to you and then you cash it and get the money from it to give to them.
If the check is in the strangers name then they could endorse the check over to you so that you can cash or deposit the check in your checking account.
However be aware that if you do cash a check for a stranger that they endorse over to you and it turns out to be a bad check then you'll be on the hook for it.
I would highly advise against cashing any checks for strangers because there are fraudsters out there that ask strangers to cash checks for them and then they take off with the money and it turns out the check is bad.
If the check is bad the bank will remove the amount of the money from your checking account or demand you pay back the money for the cashed check.
So while you can cash a check for a stranger you should never do it.