You can't go wrong with a classic! With a wide range of drinks (and regular seasonal additions to the menu), snacks and sandwiches, Starbucks is always a great go-to.
Plus, this spot is particularly nice -- located right at the base of one of the most popular meandering streets in the city (Piotrkowska), this is the place to grab a drink and a good bite (some delicous sandwiches are found here) before heading up the street for some sightseeing.