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