will taking some preworkout mixed in water break my fast?
Sucralose frequently is combined with dextrose which gives it a positive calorie count. Splenda for example had 4 cal per gram. Check the ingredients for Maltodextrin or dextrose. If they are present you’ve likely got a fast breaking pre workout mix.
Some people say black coffee breaks a water fast so its really up to you on what type of fast you are doing. Will it show down your fat loss? I doubt it. CICO. It might cause you to gain water weight though.