The eponymous coffee meeting that turns into a negotiation is based on sound science. [vi] Getting someone to hold a warm beverage is influential.
Warm beverages (e.g., tea, cocoa, coffee) increase agreeability. Soothing behavior involves holding a warm beverage.
This may be handled by beverage selection. It may sound ridiculous, but get hot coffee or ice tea in your adversary’s hands, depending on your intent. Be self-aware when you are getting your own caffeine fix.