You do have this found cat with you at this moment right? He is hungry and the shops arent open yet?
Try to give him something... Preferably a little but of several so he can choose. You will see if he eats anything of it. Vegetarian food isnt poisonous, it is simply not sufficient for cats.
Btw. Common milk may be not good, better with low-lactose milk. Water is best.
Otherwise most easy is to go to a shop and buy cat food. Easiest dry food, as you can keep it, and use when the need arises. Do have it well closed, no contact with air - air destroys.
If are buying some cheap brand, as is the most common in the usual food-shops, take their Kitten variation. Or their variation for active cats. These have more nourishment.
As for giving food to loose cats on the campus area - you had already got some good answers.
Giving the hungry food is nice. But it will be really good firstly when you have a plan with it. It is best if you are part of a network.
Besides, there is also a risk, if any of them DO belongs somewhere. If such free roaming a little shy home cat gets food outside, there is a risk he dont returns home... More then one homeless was made this way.
So IF you give food, be sure they are homeless or otherwise in need of help.