I liked how you did your experience. Having several snacks and drinks, you could compare and contrast the different features. It was analytical and methodical.
I wish you would have said where your insights specifically came from. For example, saying that teachers always prefer healthy snacks over unhealthy snacks was from the observation.
What if you tried interviewing a male. Male and female caretakes have different ways of doing things. By interviewing a male, you may have been able to uncover a different kind of insight.