It depends on what type of shop it is. If it's a building, I'd call it a snack shop or even a little restaurant. However, if it's something else, like a kiosk or a mobile van, then you'd need to use the appropriate word.
If it sells all the things you listed, it wouldn't make sense to call it a "fries stand/stall" or a "sandwich joint". A "snack bar" would probably work. A "nibbles shop" is unnatural. A "tuck shop" has a very specific meaning in BrE - it's where young schoolchildren go (inside the school building) to buy a snack during their break time. We had a tuck shop at my primary and junior schools but not at secondary school. At the first two schools, it was located in the canteen but the food was sold from a small table set up in the corner, rather than from the long counter where our lunch was served.
