Need ROKU for this.
I unlinked and relinked my roku streaming stick from my roku account. 2 days later I got email saying,
"based on the activation date of your Roku device, you may be eligible for 1 month of DirecTV NOW. Click here and enter your code: ROKU*********. In addition, you may be eligible for 1 month of SHOWTIME, go to your device and see if you qualify."
I opened directvnow, signed up new account and at checkout I entered the code and it worked. I tried it on $70 subscription total due today was $0. It should work with any plan.
Possibly you can get Showtime too but haven't tried it.