Cross Apply in SFMC SQL Query Activity

Question

SELECT
  e.cust_id AS customer_id,
  e.event_id AS event_id,
  max(t.updatedON)  as recent_timestamp
FROM
  event_table AS e
  INNER JOIN car AS c ON e.cust_id = c.cust_id and e.event_id = c.event_id
  INNER JOIN walk AS w ON e.cust_id = w.cust_id and e.event_id = w.event_id
  CROSS APPLY (values(c.updated_On),(w.updated_on)) as t(updatedOn)
  group by e.cust_id, e.event_id

Error: An error occurred while checking the query syntax. Errors: The values(values(c.updated_On table has a multi-part specification. This is not allowed. values(values(c.updated_On is not a known data extension or system data view. You can only query existing data extensions or system data views.

The three data extensions event_table, car and walk do exist. Any ideas what i can do to resolve?

EDIT: Included sample data and desired output here.

EDIT 2: The accepted answer below is correct and should remain for helping others. Since the implementation however changed OUTER APPLY to act as INNER JOIN, I did some cleaning:

SELECT e.cust_id, e.event_id,
CASE 
  WHEN
    car.updated_on >= motorcycle.updated_on and car.updated_on >= walk.updated_on
      THEN car.updated_on
  WHEN motorcycle.updated_on >= car.updated_on
      THEN motorcycle.updated_on
  ELSE walk.updated_on
END as updated_on
FROM
  event_table AS e
  INNER JOIN car AS car ON e.cust_id = car.cust_id
  INNER JOIN motorcycle AS motorcycle ON e.cust_id = motorcycle.cust_id
  INNER JOIN walk AS walk ON e.cust_id = walk.cust_id
WHERE
  e.event_id = car.event_id
  AND e.event_id = motorcycle.event_id
  AND e.event_id = walk.event_id

Answer 1

I only see two updatedON values. If you only need to find the greatest of those two then you could do something like this:

select
  e.cust_id customer_id
, e.event_id event_id
, case 
    when c.updatedon >= w.updatedon 
         and c.updatedon >= m.updatedon then c.updatedon
    when w.updatedon >= m.updatedon then w.updatedon
    else m.updatedon 
  end recent_timestamp
from event_table e
outer apply (
  select 
  max(c0.updatedon) updatedon
  from car c0 
  where e.cust_id = c0.cust_id 
  and e.event_id = c0.event_id
) c
outer apply (
  select 
  max(w0.updatedon) updatedon
  from walk w0 
  where e.cust_id = w0.cust_id 
  and e.event_id = w0.event_id
) w
outer apply (
  select 
  max(m0.updatedon) updatedon
  from motorcycle m0 
  where e.cust_id = m0.cust_id 
  and e.event_id = m0.event_id
) w
where m.updatedOn is not null
and w.updatedOn is not null
and c.updatedOn is not null

The OUTER APPLYs are acting like LEFT JOINs but with the criteria inside.