He needs a part time job at uni, and as many jobs as he can get in the holidays to earn money to live on.
I foolishly picked nice but expensive uni accommodation (in a cheap northern city fifteen years ago, mind) and I had to pay my accommodation costs myself using my student loan, as my parents couldn’t afford to pay it for me.
They sent me £10, £20, occasionally a bit more whenever they could, but were really hard up then. My DGM was generous and better off, so sent a few £100 every few months, but it doesn’t go far. I was foolish and drank and partied too much - he’ll need to be more frugal.
Please don’t feel bad if you can’t afford to send him money - lots of parents are in the same boat and your son deserves to go to uni the same as everyone else.
Unis and often student unions have hardship funds for hard up students - make sure he researches all this, as well as seeing if any scholarships or paid prizes exist at his uni.
He’ll muddle through - everyone does- but he must find work in the holidays, and term time if it doesn’t interfere with his studies.