Any number of things are possible to earn a few bucks on the side. You could paw through the recently donated books at your local thrift stores to see which ones are underpriced compared to their Amazon value, buy them, and resell them. You could do tutoring for students at a nearby school. You could become a handyman, fixing things on nights and weekends. You could find a part-time job in food service. You could apply for part-time jobs that are popular with students, since they tend to have somewhat flexible hours.
Think about it for a few minutes, something will come to you.