Different ways to clear SQL Server Memory

DBCC DROPCLEANBUFFERS

Use DBCC DROPCLEANBUFFERS to test queries with a cold buffer cache without shutting down and restarting the server.

USE METRIC_DATABASE;
GO
CHECKPOINT;
GO
DBCC DROPCLEANBUFFERS;
GO

Ref:

https://www.mssqltips.com/sqlservertip/4714/different-ways-to-flush-or-clear-sql-server-cache/