In the US, never. I notice that they are not at any of the bona fide charities. There is a reason for that. The charities do not hand out cash - and for good, prudential reasons. Money cannot help those with drug, alcohol or mental health problems. Only a certified charity with the resources to assist can help them.
We are called to use the virtue of prudence in dealing with such people. IME of 31 years encountering them in an official capacity, I know that many are fakes, alcoholics, drug addicts, sex offenders, but many are also mentally ill. Giving them money helps them to avoid dealing with their difficulties.
Our priest refers those in need to the regional charity coop.