Drop all foreign keys

DECLARE @SQL varchar(4000)=''

SELECT @SQL = @SQL + 'ALTER TABLE ' + FK.TABLE_NAME + ' DROP CONSTRAINT [' + RTRIM(C.CONSTRAINT_NAME) +'];' + CHAR(13)

  FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C

INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK

    ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME

INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK

    ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU

    ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME

INNER JOIN (

            SELECT i1.TABLE_NAME, i2.COLUMN_NAME

              FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1

             INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2

                ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME

            WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY'

           ) PT

    ON PT.TABLE_NAME = PK.TABLE_NAME

EXEC (@SQL)

PRINT @SQL

Source: StackOverflow