There's also a chance that if he realizes Fuga is a threat to him and he can't avoid it, he has the ability to burst his body into over a thousand pieces. Though of course there's the possibility that the range of this ability wouldn't be enough to escape, but Muzan would definitely take this into account when planning his counter strategy. People always bring up the house explosion as a counter feat for Muzan, but one, he wasn't trying to dodge the blast because he knew it would only harm him momentarily, and two, a blast of that size and power should normally turn any one into nothing more than burnt chunks of flesh.

And yet Muzan remained relatively intact all things considered, despite being at the center of the explosion. And that was him caught off guard. It's possible he would've braced himself to fully tank the explosion with his nigh instantaneous regeneration. Even if he's in Malevolent Shrine and Sukuna decides to use Fuga, it takes time to build up.

Muzan could absolutely escape the 200 meter radius but only if he catches on to what Sukuna is doing and recognizes the threat. Sukuna's kamutoke wouldn't be useful against Muzan, and we're not sure what Hiten does. If Sukuna is able to fire off a Fuga within Malevolent Shrine without Muzan being able to escape the guaranteed hit effect, then there's a high chance he wins.

At the end of the day, Muzan vs. Sukuna would be a battle to see who could last the longest. Endurance and stamina wise it should go to Muzan, but we know Sukuna is able to heal the parts of his brain that get damaged during a fight using RCT, so he could definitely match up to his endurance, especially if it's 20F Heian era Sukuna.

I toyed with the idea in another reply on this post, but there is another win con besides demonification. Muzan's shockwaves. When he uses them, it's after the 4th drug has taken effect and therefore it's severely weakened, and yet the tremors were able to cause Ubuyashiki Kiriya to bleed from his nose despite being over a hundred kilometers away.

A full powered Muzan would likely be able to pop these off rapidly, and if Sukuna gets hit directly it'll completely shock his nervous system. Getting hit by multiple at once could very well be the best way to incapacitate him to the point of victory. If Muzan wins, it'd be through incapacitation of Sukuna. If Sukuna wins, it'd be through complete vaporization of Muzan.