For me this is one of those obnoxious "it depends" situations. Personally, I only Instagram my food if it serves a narrative purpose...like "Hey look, I'm eating scrambled eggs at midnight because I got hungry after our movie marathon!" I guess I also Instagram it if it's particularly pretty, but that's the photographer in me. Otherwise, it seems disingenuous.
I try to do as much brand research as I can before I go, and usually try to compare it against what coupons (both physical and digital) I have. I'm not a huge brand loyalist, so sometimes this can trip me up, but it's better than standing in each aisle for 5+ minutes reading the back of the product! (My biggest research point is checking for companies that don't test on animals.)