I have fasted for three straight days on many occasions and it was pretty easy for me. Drinking zero-calorie beverages (coffee, tea, water) should be fine. This is not professional medical advice and definitely do not do this if you are an alcoholic, diabetic, or pregnant. Once you break the fast, do so with moderation.
The "killer feature" is that they pay more to the developers, so if you are getting the exact same game on (e.g.) Steam versus Epic Games, then whomever actually made the game gets more money from the Epic sale. Isn't that a good thing?
(Note that I may be conflating the publisher with the developer, but either way, it's still the case that less money is taken by intermediaries, which is a good thing.)