All the canteens of Sun Yat-sen University are open to the public. You can buy meal tickets in cash. The price is 25% higher than that of students in our school. For example, the student card only charges 6 yuan for meals, so you need 7.5 yuan in cash. So I suggest that you'd better ask the students to swipe your card for you, and then you give the students cash. Generally speaking, students from CUHK help.