I also have sling tv and had no problems with it. Just ESPN
I also have sling and do have any problems watching ESPN programs on it but ESPN alone gives you more sports but I can not get different games when I am on it.
The only way you can get ESPN is by having a TV subscription. I have a subscription through Verizon for my ESPN subscription that allows me to stream on my TV ESPN content.
I also have an ESPN+ subscription that gives you only ESPN+ events.