Just water. I did 7-8d, walked 3x and lifted 4x, could have done more but saving energy. Was tired tho. Earlier in year? Ya couldn't do much of anything, at all. I only restarted walking again forcefully on day 8-10 and wanted to walk a bit on day 18 or so. And then as I recovered, got back to the gym. That was Jan to Feb, refeeding thru march and Randro and 4andro started.
Honestly, true muscle wastage will take a while, and after a fast... you're primed to gain. Losing 2-3lb LBM (depends on a person's size) is not a big deal at all. I mean I lost and gained 30-40lb last year which was crazy. Normally 180-186, now there... 191-194 but much stronger. Randro, 4andro at times 199 and jacked. But now natty, and post water fast was 186, quickly gained back to 190. however, clearly sometimes I gain and lose rapidly. Which is kind of odd... but makes sense. Never rapidly enough tho!
Running and weights are fine, but less intensity. And don't push too hard. Like maybe if lifting 5-6 times, only lift 2-3 x and maybe 38-40 mins rather than 50mins. Maybe instead of jogging or running 20-30mins, do like 15-20, or instead of 10-15 intervals, like 10. Scale down. Keep hydrated. It rips you up in good times.
Didn't really rip me up first fast, but slowly over months helped a ton. Definitely lost a fair amount of fat and water then, but still had 8-12lb water and fat to get rid of. Gone, cut fat, and jacked up. Mostly look ripped. SOmetimes think fatter than am, but I'm pretty sure it's normal to not look 100% lean all the time, like after eating. It's getting to strange ideals now.
Good Luck on The Fast Mate. Will be worth it. Should see results quickly but don't get discouraged if you feel the same only skinnier with no digestion and tired for 5-10 days. etc.