Have you got a list of the macro variables? If so, you can write a code object to reassign null, zero or missing values as needed to these using %Let in open code statements, or in a data step with Call Symput() . Then call the code object as needed.
You can also interrogate the SQL Dictionary table for macro values, but this requires you can identify the macro symbols that you wish to null out.
There is also (since version 😎 a SAS macro function called %SymDel that will delete symbols from the symbol table. There is documentation on the support website and in the online help.
Kind regards
David