How to add time to DateTime in SQL

Try this

SELECT DATEADD(day, DATEDIFF(day, 0, GETDATE()), '03:30:00')

For me, this code looks more explicit:

CAST(@SomeDate AS datetime) + CAST(@SomeTime AS datetime)

Try this:

SELECT  DATEDIFF(dd, 0,GETDATE()) + CONVERT(DATETIME,'03:30:00.000')