Ask support to connect the 2 instance and you will be able to import programs from one instance to another. Ask support to specifically establish a 2-way connection between the 2 instances.
When you import/ copy a program, you will be prompted to set a few options that will enable you to copy the necessary templates and channels.
There are some imitations, though and sometimes, the import will fail without much of an explanation. I have observed that programs which leverage a shared asset (such as a form from the design studio) do not copy well.
There is no such in Marketo as a sandbox refresh (as you would do in salesforce).
The only thing you can do it to ask support to connect your 2 instances, so that you can import programs from one instance to another. Programs will import with them the templates and the channels, but a lot of things will have to be duplicated manually.