I quite like SIS but here in the UK I find High 5 offers more bang for buck, their Lemon with Caffeine powder is my favourite. I could do with drinking more though but thats a generic thing and nothing to do with a specific drink; a whole bottle will disappear on trainer, whilst often outdoors half the bottle is left when I get back 50-60miles later.
Flow Formulas works great for me. Good taste, goes into solution pretty easily, and easy on the stomach. I’ve tried the Skratch High Carb in the past because I’ve always liked their stuff, but it was always a pain for me to get into solution.
But man, that schitt is expensive so I have been using Tailwind a bit for training and saving Flow for big days / races. It is OK, but I definitely prefer Flow.
Untapped.cc here - their gel mix. I used to use Skratch high carb mix, but after a while the flavor and the long prep time (need an hour for the powder to dissolve) really got to me.