Sql Server has an option of navigating to all tables using stored procedure sp_MSforeachtable
For e.g the following command will drop all the tables in the database:
exec sp_MSforeachtable 'DROP TABLE ?'
The below command will clear all the tables:
exec sp_MSforeachtable 'DELETE FROM ?'
So by using the procedure sp_MSforeachtable you can navigate to all the tables and do your task like cleaning table, dropping table etc.
If the database is no longer use, so far you may use this command also:
drop database <yourdatabasename>
Or you may use GUI feature to drop table from one database one by one!