According to Geno the chef in the aftershow. He said this new concept of street food is prepared on the spot, where you see them quick frying the gourmet ingredients, like they showed in the clips at the start.
Not the prepared and reheated stuff both teams produced. So they both failed the brief and Sugar should have pulled them up about it.

My guess would be that this wouldn't have been mentioned in the brief so both teams assumed they could pre-cook it. Since it wasn't mentioned at all throughout the regular episode, I don't think the candidates were aware that they had to cook it whilst they were there.
Wish they had, though. It would have made for some funny moments!

That's what I was thinking . Would have been far more entertaining.

I agree. However you have to be licensed to sell food and since they only had a day or so, I suspect the show got around it by having the food prepared in a restaurant which was already covered. The council wouldn't have been happy licensing people who didn't have proper food safety training and would have been preparing high risk food for sale. At least this way they knew the food was safe to eat, would have made it much easier to make it legal.

Yes. When I hear street food, I imagine something like panini (if you wanna go Italian), or pad thai (anything noodle based food Thailand style), chicken satay, French-Vietnamese baguette (quite popular in Paris & London), croque monsieur, crêpes, a kind of cheese bread in Brazil, etc.

The thing is those food I mentioned above are not "fancy" street food that Lord Sugar specifically stated.

Exactly! The license is very difficult to obtain for street food vendor here.

So really the big spiel he gave at the beginning about this new concept was misleading. Street cooking is not new in far eastern countries but they would need more training then the show allowed I guess.