Why are you passionate about solving water resilience issues, and why do you think your idea will make a difference? Five groups of students from Brazil, China, Ivory Coast, India, the USA, and Europe spent two weeks in an online workshop organised by the IdeaSquare team at CERN. They went through lectures, workshops, and daily assignments using design thinking, among other innovative methodologies, to polish and prototype their initial ideas. These teams were the finalists of the first call for ideas of the Crowd4SDG project, which gathered more than 100 students worldwide. The Crowd4SDG consortium (UNIGE, CERN, CSIC, IIIA, Politecnico di Milano, UNITAR, Universite de Paris, and CRI) promotes citizen science for the SDGs, focusing on Climate Action. Its goal is to assess the usefulness of practical innovations developed by the teams and research and investigate how AI applications can enhance and provide effective monitoring of SDG targets and citizens' indicators. The initiatives organized by Crowd4SDG follow a robust innovation cycle called GEAR (Gather, Evaluate, Accelerate, Refine). The GEAR cycle started with an online selection and coaching of citizen-generated ideas for climate action in autumn 2020. The most promising projects were accelerated during a Challenge-Based Innovation Workshop by IdeaSquare at CERN in January 2021. The two top projects will be further refined at the annual SDG conference to boost their path towards creating real impact. "After two weeks of watching the participants working hard, it was very inspiring to hear them say they now believed that if they put their heart to it, they really can make a difference." - Laura Wirtavuori, IdeaSquare at CERN." The one-pager of the projects is available on the Crowd4SDG website.