@killyourfm My favourites are Kavárna Spolek (Orlí 22), Kafec (Orlí 491/16), V Melounovém cukru (Františkánská 17), Coffee Fusion (Jánská 460), or Cafe Momenta (Zelný trh 314)
All nicely located in the centre.
In brackets you have the street for better search. Or I can add links to Google Maps if you want. :)