Which jobs qualify as "related to study" on an OPT work visa for a Business Administration degree?

Hi, I am a recent college graduate and have started working in the US with OPT status. I have a job as a Business Analyst in a corporate office, but am trying to save up for grad school and was interested in getting a second job on the weekends, if possible. After doing some research I found that I could work more than 1 job as long as they both relate to my area of study. I am a Business Administration major, which is very broad and covers a wide array including HR, marketing, finance, sales, communications, etc. For example, could I work as a sales associate in a retail store since I studied sales? I do not want to violate my visa status, but am looking for any way possible to make additional income with my very broad degree!