Posted: 24/07/2015 at 09:00
Hi Mark, you might get more replies if you post this in the Ultra forum.
This is really variable, depending on weather, how much you sweat (some people just sweat more than others do), what tastes you do and don't like etc. Personally I hate the aftertaste from any of the big, flavoured electrolyte tablets (high5 etc.) so I use Elete (liquid concentrated electrolytes) - added advantages (a) you can just squirt in a bit more if you're sweating a lot; (b in an emergency you can squirt it directly into your mouth and wash it down with a mouthful of water; (c) no frothing or waiting for the tablet to dissolve; (d) if you forget to rinse out and dry the drinks bladder it doesn't start growing algae...
Some people prefer S-caps.
Re. volumes, some people will drink little and often, others prefer larger quantities less often, and how much people drink is highly variable. It really is a matter of practicing on your long runs and seeing what works for you. Too much and you'll be stopping to pee all the time. Too little and you'll get dehydrated and feel very tired.
I found that as I got more used to long runs, I started drinking less (and could go for longer without fuel intake - I completed a training run of about 26.5 miles a couple of months ago on no food during the run and less than a litre of fluid intake - but I'm 48kg and it wasn't a baking hot day, and there's no way I would have done that in my first year of ultrarunning. (And I did have food with me in case I needed it, and a couple of chances to fill the water bladder if I'd needed to).