Toma Café is one the best coffee place in Madrid, they have got variety of options and customisations. Their Wi-Fi is great and free too! The place is spacious and has all day menu.
Utopic_us US3 is a modern and fully furnished working space which is centrally located. Wi-Fi is good enough with speed up to 30mbps. You can hire a desk for yourself, public transport like metro can be used to get here.
Crystal is an electronic store where you can buy a local sim card, select the plan and the friendly staffs will help you with whatever you want.
Cespedes Coworking is a cozy little space built in a factory building with high ceilings. It has all the basic amenities needed and has many events taking place. The internet is not that great, speed is about 4mbps.
Great, clean, quiet and super convenient co-working space. Very good atmosphere with stable WiFi.
Bicycle Cafe is one of the best co working space with laptop friendly and reliable wifi. Great place for a coffee or lunch. Nice setting, friendly staff and just around the corner of big street in Madrid. Met some nice Digital Nomads here.