I'd say Fiona is right.
If you don't have a gel handy, then a good slug of Coca Cola works almost as fast. (The real stuff of course - if you've bonked then you want the sugar, not sweetener!)
I bonked near a road junction once. My blood sugar was so low that I couldn't figure out how to cross. Fortunately, we were 50 yards from a supermarket so I waited with the bikes while my riding partner bought me a Coke, a sandwich and a bag of crisps. It was 10 minutes after I finished that lot before I wanted to get back on my bike, and over an hour before I really felt my strength starting to come back.
After you've got yourself moving again, you need to keep refuelling to make sure you don't bonk a second time.
After
my worst bonk ever, I slept for 13 hours straight to recover from it!