Almost all commercial electrolyte drinks eg Nuun tablets caused me gut problems. I realised they contain artificial sweeteners or preservatives or both, and I'm sure they are the cause.
MyProtein used to sell a cheap electolyte powder that had no additives, just 4 plain salts. It didn't dissolve very well but I just gave it a good shake. Compared to just water, I found I needed to drink less because I was retaining the fluid better and peeing a lot less, so didn't need to carry as much (or stop so often....)
Of course, they have discontinued it!
If anyone knows where I can get straight salts without all the additives, I will be really grateful.