they can get bitcoin in paper form like what you get when using Bitcoin ATM.
pieces of paper with public and private address after that they can import the private key to any wallet "just show the private key to any scanner" and get the money.
Important point
you must have some knowledge and internet access to use bitcoin.
The system of of transaction with the used of bitcoin is powered by the blockchain so technically beggars who want to access bitcoin needs to have a basic knowledge about the internet where they could access cryptocurrency in the first place. Yet, gaining proper and enough knowledge for them to have the best way to earn or to start an investment with bitcoin and other cryptocurreny.
Instead of focusing them to learn bitcoin, why not do and start little things for them to learn and earn, not all beggars can read and write so there is no way for them to access it, so it is better to bring them to a company who accepts beggar and teach them how to do work, dress them up.