What plan do u guys recommend for big sugar 100 miles? It has more climbing compared to unbound total of 6-7k elevation. For unbound 100 miles i used gravel increase ftp. Through the race i thought i reached my limot around the 4k ft climbing then was struggling a bit, although this unbound had alot of mud and carrying the bike. Previously my unbound plan was for 6 months were i did 3 hard intervals for 1 hr and 1 endurance day. Should i be increasing thr time on my threshold or sweetspot training? Is the road climbing, increase ftp option worth it for this event? Tnx!
I’d put Big Sugar on your calendar and build an event-based plan.
A gravel plan will likely prepare you pretty well. Just follow the volume recommendations that we suggest and use the Check Volume tool every so often to see if we’d recommend changes. 
Sounds like you already have a solid base coming off Unbound, especially dealing with the mud and hike-a-bike sections. Big Sugar’s climbing profile will probably reward sustained power and fatigue resistance even more though.
I’d agree that a gravel-focused plan is still probably the best fit overall, but adding a bit more sustained threshold or sweet spot work could help with those longer climbing efforts. Gradually extending time in zone rather than only increasing intensity might make a big difference for the later parts of the race.
Also worth remembering that Big Sugar tends to be punchy and constantly rolling, so durability over several hours is huge. Sounds like your consistency over the 6-month build helped a lot already. Interested to hear how your prep goes this time around!