The accelerated digitisation of society has consolidated data centres as pillars of the global economy, but at the same time has increased their energy and environmental impact. Green computing has thus moved from isolated optimisations to holistic approaches, yet there is still a lack of systematic analysis of the interdependencies between the various sustainability strategies. This systematic review, structured based on PRISMA guidelines, aims to fill this gap by identifying, classifying, and critically evaluating sustainability practices applied to data centres and cloud computing. Twenty-two articles published between 2015 and 2024 were examined, selected from the ScienceDirect, SpringerLink and IEEE Xplore databases. The summary of the results shows the evolution from a strictly internal approach, based on virtualisation and the Power Usage Effectiveness metric, to a systemic perspective that integrates renewable energy management, physical infrastructure optimisation and governance mechanisms. It is clear that the most effective strategies transcend mere technical optimisation, incorporating geographical choices that facilitate free cooling, waste heat recovery and the assessment of financial risk associated with energy volatility. It is concluded that annual carbon neutrality metrics are insufficient and that hourly carbon accounting is a requirement for rigorous assessments. Future research should develop integrated optimisation models, quantify the complete life cycle of equipment and validate these principles in PaaS and SaaS models.