You could read the file in a variable and concatenate it to the message body:

DECLARE @body NVARCHAR(MAX)

SELECT @body = BulkColumn FROM OPENROWSET (BULK 'G:\MySalesReport.htm', SINGLE_BLOB) a

EXEC msdb.dbo.sp_send_dbmail

@profile_name = 'TestProfile',

@recipients = 'abcd@gmail.com',

@body_format = 'HTML',

@subject = 'Test Email',

@body = @body;

You will have to enable ad-hoc distributed queries to make it work:

EXEC sp_configure 'show advanced options', 1

RECONFIGURE

GO

EXEC sp_configure 'ad hoc distributed queries', 1

RECONFIGURE

GO