Pretty much everything I consume. The main exceptions are canned tomatoes (the store brands are always sourer than I'd like), some cheeses. I used to also buy brand pasta, but ever since my supermarket got its own generic bronze-cut pasta I no longer need to.
When it comes to medicinal products I'm more likely to get a brand version though, e.g when the brand version works better, like with Tiger Balm, or when a generic isn't available.
Have you considered he might just have a non-standard gender expression? It doesn't say anything about his gender identity. And even if he someday determines he's not a boy, he might be non binary or agender or genderfluid or any number of other things.
Just apologize for pressuring him, let him figure himself out in his own time.