I was a student through 2019 and worked part time in a fast food restaurant. Which do I put for my occupation?

It really does not matter.  You can choose anything that you feel describes your current situation.  The IRS only uses this field for statistical purposes.  

The IRS only uses "occupation" for statistical purposes.  It has no effect on your tax due or refund.  You can use "student" or "server" or "fast food cook" or whatever you want.