There are quite a few sugar substitutes you can use with a ketogenic lifestyle. Personally, I prefer the Pyure brand of Erythritol over Swerve. Even better, in my opinion, is Monkfruit — my favorite is Lakanto Monkfruit for granulated, powdered, and golden (brown sugar).
There is a ton of convenience to the Swerve product family, though … I do enjoy their packaged cake mixes.
Fortunately most sugar substitutes, depending on which one you use, can be used 1:1 as you would sugar.