KeepingYouAwake is a Caffeine clone for OS X Yosemite. It is a menubar utility that can be activated to stop your Mac from going to sleep.
This is a great utility for people who have their Macs set to sleep but may be doing a task where they don't want it to sleep and don't want to have to go and play with the energy saver settings just for one task. Just toggle state direct from the menubar.
It also supports dark mode so unlike some of the current apps that haven't yet given us a light icon you can easily see it in the menubar when you have dark mode enabled.
Download the latest version from here.