In order, the biggest two things they seem to look for are:
(1) Cultural fit. Definitely look up Workday's core values before an interview.
(2) Your thought process. I struggled a lot with the technical questions, as I had no prior experience with UML diagrams, but they seem to look more for your thought process rather than the correct answer right away.
I talked to a hiring manager at my university's career fair, and we scheduled an on-campus interview. At the interview, I think that my answer to the first non-technical question was good: I said that the number one thing I look for in a company is the kind of people who are there, and number two is a place where I can learn and develop my skills. Turns out, that exactly matches Workday's top core value: its people. Honestly, that must have been what carried this first interview, because I struggled a lot with the technical questions after, which were UML diagramming. I only managed to answer the most basic out of 3 questions correctly after much help from the interviewer, who was the same manager.
I thought I would be rejected right there, but not only did they email me for a second-round phone interview, they also sent a follow-up email a week after when I somehow missed the email (ouch). This second technical interview I was better prepared for, but definitely still needed the interviewer to help me walk through the problems. I received a call a week later saying I had an offer.
Overall, everyone in the recruiting process was super friendly, encouraging, and helpful. I'm really grateful to my recruiter for following up with me even despite my own clumsiness, and I can say that this caring attitude was very representative of my whole internship experience. The technical questions were hard (At Berkeley, we cover UML in one optional class for about a week), but the interviewers are very forgiving and (seem to) look for thought process over correctness. Culture fit matters a ton, and Workday's proud of it- don't underestimate the importance of your behavioral questions! Imo, that's what got me in.
Also, a shoutout to the intern experience as a whole - I can say that every intern here I've talked to loved their teams.