Is there a DD214 equivalent while still in active duty?

Yes/No - There isn't an equivalent to the DD214 if you haven't had a previous period of active duty service.

However, your employer is probably asking for the DD214 to verify military service, but you'll have to ask the employer about that. A couple of alternate ways are:
● You can use your LES to show you are currently a member of the military
● If they have an account on the SCRA website*, they can do a records verification on you
● Memo from your command attesting to your service with contact information
● Use the DD-2586* (VMET) from milConnect

Depending on if this is an initial application that you're submitting, I would go with a letter from yourself explaining that you won't be issued a DD214 until you separate, include one of the other forms to show your current military service, and have your contact information listed if they need anything further.

If they are sticklers on it, then you won't be able to provide one until you seperate.
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* SCRA verification page - https://scra.dmdc.osd.mil/scra/#/home
* VMET - https://milconnect.dmdc.osd.mil/milconnect/protected/portlet/dodtap

That's a helluva good question and you'd have to ask the prospective employer what they need. Obviously, if you are still on active duty and a sergeant, the character of your service is "Honorable." If they need proof of your skills, you could provide certificates awarding your MOS(s). As an officer, I wrote letters of recommendation to those serving under me. In many cases, the person had not yet contacted any prospective employers and I would include an outline of the types of information found on the DD-214. Hope this helps.

If they are asking to verify your status, show them your ID. If they are asking for proof of training/experience, your JST should suffice?

SGT (Join to see) -- Yes. It is called an Enlisted Record Brief (ERB) or an Officer Record Brief (ORB). That's it. It covers everything in your Personnel File--same as the DD214 once you retire.

Do up a statement of service MFR and get your company commander to sign it. If it is for a government job, it will need your "character of service" which reflects an anticipated "honorable" or "Under honorable Conditions" discharge. This can be a show stopper otherwise. The USAjobs templates has an example MFR you can start with.

As COL Dan Ruder indicated, I would surmise your ERB would suffice. Get with your S1 shop if you need help accessing those documents. It would benefit you to write a good cover letter explaining that you are still active and do not have a DD214 (yet) but have enclosed an ERB that lists the same information. Years ago, we had a document that we used to verify we were on active duty in good standing. I don't remember the exact name of the form now but it was something like "Verification of Service" or similar. For all I know, the ERB has taken its place and is no longer issued.

You could use a Smart transcript , milconnect DD-2586 or your LES depending on exactly what they are trying to verify.

If you have served one complete tour of active duty, usually 4 years, every time you re-up/re-enlist, you can request a copy of your DD214 and a document that says honorably discharge. No break in service. Ask your S-1 NCOIC and see what they can provide for you. If you happen to be Army National Guard, I think the equivalent is a NGB-23. Good luck. Thank you for your service.