Seems to me like you already have a pretty good reason: opportunities are opening up in your field and Starbucks was a good stepping stone to learn some skills to carry into your desired line of work. I’d just be honest in that respect as to why you wish to leave the siren.

Regardless, good luck with you’re search!

Hm, I would say for example, you became so advanced (I assume you were/are a barista, not a SSV or SM/DM lol) in all the tasks and assigned positions that you wanted to have more challenges. After a while you learned everything that’s there at you’re hitting the plateau of the saturation / learning curve but you didn’t want to become an SSV/etc. because you didn’t see a future with the Siren as you are more interested in [insert target company’s mission and values] which differs tremendously from SBux.

That’s sth I kept thinking about for a while. SBux is geared heavily towards customer service and customer happiness and bringing together people and so on (“one person, one cup, one neighborhood” you know yadda yadda), while eg my personal mission statement is (I’m actually a scientist) to strive for excellence and optimization to create better treatment for diseases — this doesn’t apply to SBux, so you could use that. Think of your own personal mission statement what you wanna do and what your personal goal is (that potentially aligns with the target company). Hope that helps.