Hi Ophelia, nice to see you here.
I'm sorry the situation is so difficult with your brother. In my experience, keeping it about your boundary rather than about his choices is your best bet for future peace and serenity. And as we are fond of saying around here, "No" is a complete sentence.
He is an adult who has the right to live however he chooses, as are you. If he is drinking, and as committed to living off family and government assistance as you say, there are no words you can offer that will change his mind. You can merely state that you do not have any money for him, and you would appreciate it if he did not ask you again in the future.
The most loving thing you can do for him is to refuse to enable him or to keep him from feeling the full consequence of his choices. Sending you strength and patience.