ftg tags can warp anything in certain raidius, if he throws his kunai at suigetsu and he uses the hydrafication jutsu as it passes through him minato can teleport the kunai and suigetsu to a location on land e.g where he fought obito. then he just needs to summon ma and pa then stalls for time till they prepare their toad song genjutsu
or he could summon ma, pa , gamabunta or any other toad give them a kunai and tell them to put it in the toad fountain. the toad disappears and within a few minutes minato warps suigetsu to the toad fountain
or he could use space time barrier to warp suigetsu into a volcano (minato probably knew the location of a volcano during his life time) or any dangerous location like a high altitude
also minato can teleport things without touching them like he did kurama, so he teleports suigetsu to a place where there's land and summons the toad with the staff that blows up stuff on contact. also explosion tags were standard ninja tools so after teleporting to a place where theres land he just warps an explosion kunai into suigetsu
minato makes a shadow clone (standard ninja jutsu) then marks it, then the shadow clone marks minato as well; the clone easily tries to grab suigetsu (because both minato and the clone are marked it would be easy for one of them to get close to suigetsu) but as the clone is passing through a hydraficated suigetsu minato teleports the marked clone and a hydraficated suigetsu to a location on land where minato has the advantage and i believe can win.
space time barrier can warp suigetsu into the fire toads stomach where he'll digested
since he can warp things without touching them i doubt he'll loose to suigetsu since he can just warp him into the fire toad's stomach.
also minato can dodge all of suigetsu's attacks just by throwing his kunai in the air teleporting to it then landing with it on the water.
or space time barrier.
minato mid diff