Those who own a membership to Twitch Prime have access to loads of exclusive content, including free games, and the latest title available to members is Day of the Tentacle.
The remake by Double Fine is currently free for those who own a Twitch Prime membership. Day of the Tentacle can be picked up here until August 8th, 2017. Once you get the game, add it to your Twitch library so that it can be downloaded and played via the Twitch desktop app.
Day of the Tentacle Remastered is available on PS4, PS Vita, and PC.