thanks and yeah, it was really sweet and it made me feel cared about

I did end up replying.

The next day after I went to the store I just texted him a pic of the bottle as a reply.
I figured it was a reply that he would know what it meant ("see, I'm making good choices like we talked about and doing this thing I should be doing for my health") and showed that I got the text and appreciated it, but wasn't like a wordy reply and it didn't really require a response. I didn't want it to seem like I expected him to do therapy type stuff over text or like I was asking anything of him. I kind of hoped it would make him smile/feel proud.
He replied with a thumbs up emoji.
Seeing him again today.