SQL Server 2008R2 Database refresh in isolated environment
Just restore them over top.

RESTORE DATABASE db1 FROM DISK = '\\share\folder\file.bak'
  WITH REPLACE, RECOVERY;


You may have to use the MOVE option if the folder paths for data/log files don't match, e.g.

RESTORE DATABASE db1 FROM DISK = '\\share\folder\file.bak'
  WITH REPLACE, RECOVERY,
  MOVE 'data_file_name' TO 'D:\SQLData\file.mdf',
  MOVE 'log_file_name'  TO 'E:\SQLLogs\file.ldf';


You can get the file names (and anticipate their sizes, too) from:

RESTORE FILELISTONLY FROM DISK = '\\share\folder\file.bak';