Sustainability and Shariah compliance share a natural affinity, and the Gulf Cooperation Council (GCC) has become a centre for the issuance of green and sustainability-linked Sukuk that combine the two. For an issuer, structuring sustainability into the capital stack through these instruments can widen the investor base, lower the cost of capital through a sustainability premium, and align the financing with strategic and regulatory priorities. This paper examines ESG-linked Sukuk and green instruments as a financing tool for GCC issuers. Using an indicative dataset calibrated to 2026 conditions, it sets out the families of sustainable instruments, the structure that combines the Sukuk and the sustainability features, the benefits the instruments offer, and the requirements they impose. It develops a framework for when an issuer should use a sustainable instrument, examines the perspective of the sustainability-focused investor, and addresses the risk of greenwashing that the instruments must avoid. The analysis finds that sustainable Sukuk can widen the investor base and deliver a modest pricing benefit, the greenium, while aligning the financing with strategic priorities, but that the benefits require genuine sustainability substance and rigorous reporting to be realised and to avoid the reputational risk of greenwashing. Three indicative case studies, a sensitivity analysis, an international comparison and an implementation roadmap support the analysis, which is intended for GCC issuers considering sustainable financing.