Generally speaking, trackside food tends to be pretty pish. I liked a Gran Marnier Crepe until they stopped doing the chocolate option a few years back. We started doing them 'right' on the campsite with melted Terry chocolate orange!
Worst and best were both on a rally sometime in the late 1990s- probably the RAC.
The best was a burger in Dalby woodyard. Spotless van, home made local farm shop beef burger with proper cheddar and sweet onions, a lovely fresh bun with a slight crust. Beside the van was a good sized table covered in bowls of salad- fresh crunchy leaves, cucumber so fresh you could smell it 10 yds away, salted tomato and every relish and topping you could imagine including a really smokey mayo. They were the finest 3 burgers I have ever tasted.
A few days later we had the misfortune to try a burger in Sweet Lamb, mid Wales. The van and guy serving were so filthy, the bread stale and the grease was running down your wrists. The bin was overflowing with un eaten burgers. Vile. Two of our group got really bad shits the next day and we had to head home early.
It's much better to cook for yourselves at Le Mans. The supermarkets are much better than those in the UK and much cheaper too. You can drum up a fine feast in no time if you take some basic cooking gear with you.