Hi Wiggal
I have suffered with this all my adult life (now in 50s). Many diabetes tests, all neg. About 8 years ago I got myself one of those cheap blood sugar monitors from Lloyds Pharmacy and monitored my sugar levels over a week. Swings between 7 and 2.5 mmols - the lower ones when having this kind of 'hypo' event.
At around the same time, I found a website that described my experiences exactly (website has since disappeared) and the way that the writer had managed it - I have tried it and it works for me.
The three basics for me are protein intake, high roughage/ low sugar, and exercise. So if I do not have some good lean protein at breakfast time and at lunchtime, I will inevitably experience a hypo in the afternoon. If I don't have vegetables and keep on the move, it is more likely than less likely that I will hypo, but the protein is the key.
Taking in sugar, in coke, chocolate or dried fruit gives a brief lift but just makes it all more likely to happen, overall.
In fact the only time I was able to diet and lose weight successfully was by following the Atkins regime - I wouldn't advise it, but it was noticeable that for the first time I could go without food for long-ish periods and not have a hypo.
I try to stick with small, regular meals with high protein and roughage, low sugar content - and this means the hypo's don't happen. Give it a whirl and see if it does the same for you - but also see your GP as others suggest.