I used to have a routine for big races that didn't involve bonking, but did have me riding when very carbo depleted. Say I had a Cat 1,2,3 100 mile race on Sunday. A big race for this Cat 3 back in the '70s when there were just not enough long hard races. I'd ride 120_ miles the Sunday before. Carbo depletion. Monday and Tuesday were low carbo days, riding my usual 45 miles before breakfast. Not a whole lotta fun. Wednesday the same ride and normal diet. Thursday and Friday I tapered down the riding and ate LOTS of carbos. Fun! From Friday evening on, nothing but fruit, water and juice, as much as I wanted.
Race day, my body felt completely clean and fueled. Speed the first two hours was a little off, but if I could get past halfway, from there I just got stronger. I did this for my best race, a very fast 105 miles and hills. Wasted a lot of energy in a wasted break but still managed to make the cut at mile 90 and finish in the money and under the old course record.
Ben