I worked at a place that was serviced by a mobile espresso van. Brought very expensive coffee drinks and a standard array of over-priced donuts, rolls and cupcakes three or more times a week. Always about mid-morning. Staff treated it as a coffee break. They offered coffee drinks with frappucino, fattening sauces and so on. The woman who ran it was very friendly - I think that's key - to make a special connection with your regular customers. The woman ran it for years although the coffee itself left much to be desired.