Since 2015 there are Startup Weekends in Bremen:

Startup Weekend Bremen SPACE 2019

(covered by bremen-startups.de)

Startup Weekend Bremen WOMEN 2019

(Video 1)

(covered by Weser-Wirtschaft, page 23)

Startup Weekend Bremen 2018

(Video)

(covered by BremenNews)

Startup Weekend Bremen 2017

(covered by Weser-Kurier) 
Founded after this weekend: Cup2date (taken over by ReCup in 2020)

Startup Weekend Bremen 2016

(covered by Spiegel Online)
Founded after this weekend: Handwerksmensch

2015 Startup Weekend Bremen SPACE

Founded after this Weekend:
Valispace
SPiN
SatSearch
DisruptSpace