PepePls is a Twitch emote of Pepe looking sad while dancing side to side with his arms swinging in the air. It is usually used to express a mixture of part joy, part sadness/resignation.
This emote is a rather unknown one to this day and there are very few details as to what chats it is enabled in.
On June 23rd, 2015, user EmJaKae uploaded it to the Twitch emote extension BetterTTV. From there it has seen some use occasionally on Twitch but never gained any traction to become popular.
The main reason being not only is there other emotes that do the same job but there is also another Pepe emote that is basically the same thing.
This is usually the case when there’s an oversaturation of emotes that are used to convey the same emotion.
So the streamer you’re watching is teasing the chat a bit with some anticipated announcement, but they keep holding it off… pepePls.
You can also use it when hearing music (usually more sad tunes), or as an act of surrender/acceptance. “oh alright 🙁 pepePls”