I’ve bonked enough times that I rarely/never go out on a ride without at least SOME food on board. Even a flat 20 miles I have a mini clif bar in my pocket just in case.
I’ve done fasted rides/runs, but I usually have to top up the glycogen levels straight after, be it a sandwich, bowl of cereal or a protein shake. I try not to do that if I’m planning on doing any climbing.
And I always have a bottle of water. And these days, a second bottle with electrolytes for any ride more than 2 hours.