Can we add column to an existing table in AWS Athena using SQL query?

You can find more information about adding columns to table in Athena documentation

Or you can use CTAS

For example, you have a table with

CREATE EXTERNAL TABLE sample_test(
id string)
LOCATION
's3://bucket/path'
and you can create another table from sample_test with the query

CREATE TABLE new_test
AS
SELECT *, 'new' AS new_col FROM sample_test
You can use any available query after AS