"Will buy coffee"

"Will buy coffee" may be a nice way to show gratitude sometimes, but it rarely makes sense in professional settings.

There are absolutely times when "will buy coffee" will help you gather support for working outside the confines of existing processes and, hopefully, change things for the better.

Otherwise, you are effectively asking someone to do you a favour by circumventing processes with you. Be professional and do your work properly instead; don't use "will buy coffee" as a means to offload your responsibilities.