Depends on what you want. JUST Electrolytes or do you want some fuel to go with them?
I've been using Nuun for years now because I personally don't care to mix my calories with my electrolytes. Also I can carry a tube of Nuun tabs in my pack so if I need to top off I can also make sure there are electrolytes in there too. That said they aren't for everyone.
If you're looking for electrolytes plus carbs, keep reading the thread, 'cause I got nothing for you on that. 🤷♂️
I used OSMO for century rides, but it's pretty pricey for regular training rides.