2 options:
- Relay at Marne La Vallee train station. There is a big and a small one. In the big one they have more options for sandwiches, salads, bottled drinks are cheaper here. They also have some pastries, coffee etc.
- Take the RER (underground/train) one station to the mall at Vall d'Europe. There is a big supermarket called Auchan. It's what they call a hypermarché, I think this is basically a
Walmart. Besides groceries they will also have clothes, furniture etc. If you have a day to spare, always fun to discover other culture's supermarkets and shopping habits. At Val d'Europe there is also an outlet shopping mall for the high brands (La Vallee Village) and there is an aquarium.