like, how? are you straight up bribing people with coffee for security favors? or is it like, "hey man, thanks for helping me out I'd like to buy you a coffee but I'm busy with secret consulting stuff - here's a gift card"
Is this something that only works for short lived external consultant interactions?
By the end of a 4-5 week run you will know all the security people in a building. If I go to lunch an forget my badge they will let me back in no questions asked. This is something I used to do as staff, and still do to this day.
Its not about bribing to get a specific favor. Its about getting on good terms. Having people like you is a good thing and it makes their job a bit better and can make their day a little brighter. win-win