How can I build different projects, within the same project?

How can I build several different games from the same project without having to create different project for each game? for example, if the different game only require few changes in configuration within the same project, I do not want to create a whole new project! by this I mean a completely different game which can be built from the same unity project and not just a different platform of the same game, this includes having different entry for the project in unity cloud, etc…