The major challenges in sustainable implementation are the financial issue and uncertainties. The traditional financial budgeting approach that is commonly used to evaluate sustainable projects normally neglects future decisions that might need to be made over the course of a project. The real options approach has been suggested as a tool for strategic decision making because it can provide flexibility which can increase the project value. Researchers have been trying to identify the potential of the real options approach, and provide the frameworks for a real options evaluation and flexible strategy in sustainability improvement. However, some important variables and financial impacts explanation of real options are missing. Models can be improved to show the variation of possible project values along with its behavior. This work aims to improve the real options model in sustainable projects to provide understanding about the financial impacts of flexible strategy to sustainable improvement projects and to be used as a tool to assist decision making. The results showed that real options can have a positive financial impact to the project. The extension of this model can assist the analysis and development of decision policies.