Starbucks Coffee is a special area that is used to purchase units of Energy (in the form of Coffee) from Credits. It is located in the 6th Floor within the Government Offices in Sector 3
The cost starts off as 25,000 Credits per unit for the 1st unit, however, the cost will increase as your purchase more. The price increase stops at 500,000 Credits per unit if you've purchased 1,000 or more coffee. Each day 5% of your previous consumption is subtracted so if you abstain from buying coffee the price will go down over time.
To access this area, you must have rank 2 in the efficiency tree of your commander skills.