Nothing you’ve not eaten on a ride before.
Gells etc give some peole stomach cramps. Ditto 50:50 orange juice water for me, needs to be nearer 1:2 water:OJ for me. If in doubt go more dilute.
Cereal bars are good, especialy cheep value ones which are just loaded with sugar, avoid anything healthy, dried fruit, nuts etc contain lots of fiber and the sugar needs water to dilute it, all of which can lead to somach upsets when your energys already being used elswhere. Similarly apple skins are a no-no.
White bread, chicken/turkey and honey sandwiches are oddly nice.
Bannana’s are good.
Homade flapjack with lots of sugar in it.
Some low intensity riding the week before hand and lots of carbs during and after with protein.
Some kind of electrolyte, either in your energy drink or as tablets you can add to OJ&water. Keep you pace down, I find I sweat ~750ml/hour on my own on a short/fast ride arround 2 hours, but can get away with 1 bottle on a a 4 hour club run.