SQL Server and Cloud SQL do not support CSV files. As already indicated, SQL Server presently supports importing databases using BAK and SQL files in Cloud SQL.
The Cloud SQL versions for MySQL and PostgreSQL somehow support it.
One of the following options is possible:
Alternatively, switch to MySQL or PostgreSQL as the database engine (where CSV files are supported).
You can utilize your CSV file to create a SQL file that you may use to import into Cloud SQL, SQL Server, if the data on it comes from an on-premises SQL Server DB table.