clasher

I've looked at grocery stores on the route a few times, never seen any that were 24/7 like we have here. Most of the grocery store chains have bigger stores on the edge of town that seem open until 1900 or 2000 most nights. McDonalds might be a good place to stop and get water, there is a 24h one in Fougères on the west side of town. Back in '04 when I was in France the food at McD's was a lot better than the Canadian version, think they sell wine and beer too. Some of the big gorcery store chains are Carrefour, Aldi, Lidl, E. Leclerc, Super U et drive, Intermarché; ones I've seen along the route or close to it. There seems to be some little grocery stores along the way too but it's not always obvious what is actually convenience store and what isn't, streetview helps with that. One chain of convenience stores is called "8 à Huit" and they're open 8-20h usually. Another chain is "Coccimarket" but they seem smaller. If you stop for a meal at a bistro you can always order a "carafe d'eau, s'il vous plait" and use that to fill your bottles.

For me doing the 90h start I am gonna hope that it's a cooler night and that I don't need to drink a lot of water... will stop at any roadside coffee tables or open cafes though and inquire about water when I do... most people have drinkable tap water in France nowadays so if you're worried about that just learn how to ask for it. A lot of people still only drink bottled water and sparkling water is more popular so people there might not think to offer since they don't normally drink it.