Like lemonade stand, the challenge is to find the best mixture possible between coffee, sugar, and milk, while still having enough cups each day to serve everyone. After that, it's just a matter of finding the right price to charge depending on the weather.
If you're reputation goes up high enough, maybe even the pope will stop by for a quick drink.
The better your coffee, the more you can sell your coffee for. But for a laugh, on day 14, make the worst cup of coffee you can and sell it for as much as you can. Everyone will still stop by and since you're closing shop tomorrow, it doesn't matter if they all start puking their guts out on the sidewalk.
Play Coffee Shop at armorgames.