I arrive at CDG terminal 2A the morning of April 16. I have already purchased a TGV ticket to travel to Rennes that day (crossing fingers strike schedule doesn’t change or affect my journey). I noticed there is a store (Marks & Spencer) in the arrivals hall of 2E that I would like to go to pick up snacks before my train ride. How hard would it be for me to go there from 2A? On the map, it appears possible.

It is possible. Time may be an issue though.

It is a huge distance just to get "snacks" and I personally doubt that it is possible. If your were going to Rennes via Montparnasse instead of CDG, it would certainly be simpler for you to take the RER B into the city and buy your indispensable items at the Marks & Spencer Food shop inside the RER station at Ch telet-Les Halles. Then you could hop on metro line 4 to get to Montparnasse for your train to Rennes. The shop is on the exchange level, so you don't even have to leave the connection intercourse.

There are other snacks besides M&S, you know.

When does your plane land and train leave?

Last few times my son went thru CDG Immigration there were just a few booths open and long lines.

Why not bring snacks from home?

"There are other snacks besides M&S, you know."

Now now, be nice. Aggiegirl likely isn't a Brit so she's not living off M&S for life - not too many Brits list themselves as "aggies." An "Aggie" is the not-too-imaginative nickname for the students at, and former students of, various US "A&M" or "A&T" universities (Agricultural & Mechanical or Agricultural & Technical), the most prideful of which (for some bloody reason) are the graduates of Texas A&M University.

Im a little confused. Isn't 2E right next to the train station?

One always learns something new on this forum. All these years, I never knew there were other snacks besides M&S!

PalenQ, my plane arrives at 9:30 am and train departs at 12:48 pm. If my plane is late or the immigration lines are long, the thought of going anywhere but straight to the train will be dismissed. As a frequent visitor to the British Isles, I have become quite the fan of M&S snacks. I was pleased to learn that M&S returned to Paris and now has several locations in the city. If all goes quickly, it'd be a treat to pick up my favorite goodies to take on my Brittany adventure.

i read somewhere that the location at Chatelet Les Halles closed down in the past year.

No, it was the very first M&S to open after the renovation of the RER station. What Marks & Spencer is closing are their department stores in France. M&S Food is alive and well. I like their snacks as well, but you won't necessirly find all of the same things that they sell in the UK since their aim is to make money -- by catering to French tastes. Also, not all of the items can be sold outside of the UK because the ingredients are not always in conformity with EU regulations.

If you are coming off a red-eye flight, you may find the train promotes more snoozing than eating.
SNCF shows a buffet car in 2nd class:
https://en.oui.sncf/en/tgv/services
The Relay chain of convenience stores sells snacks at CdG and many train stations.

Sadly, I won't be snoozing. There are at least four stops between CDG and Rennes, so I'll be alert watching to make sure my suitcase doesn't walk off the train.

It has been some time since I took the train from CDG, but there used to be a snack bar, with seating, right next to the departure point. It was easy enough for us to purchase sandwiches and bottled drinks to either eat there or take on the train. Perhaps other Forum members with more recent experience can let you know if it is still there.

Keep in mind that the TGVs always have a bar/food car. Actually, the risotto they sell is not bad at all. Probably better than the sandwiches, but it's hard to be sure. A different company seems to win the SNCF food contract every few years, so if you are not a regular consumer (which I am not), it is impossible to know for sure. Do not believe anybody who says that the food on the train is terrible because they almost certainly are referring to the food sold during one of the previous contracts. The only thing that is certain is that you will pay a bit more than if you had a chance to pick up some food before boarding -- but hey, it's a train.

Yes, there is more than one place to buy food at the CDG train station.

Greetings from France. It was easy as can be to go get my Marks and Sparks goods!