An apple.

Honestly fresh carrots are so good if they're from your yard or you can get them from a local source. Store-bought carrots from several states away just don't taste the same.

Depending on your definition of prep, I would also recommend apple, walnut, coconut yogurt medley with lots of cinnamon. You have to prepare the yogurt ahead of time though (no heating involved).

If I'm just snacking for no reason, I also like to eat nori...not many calories there though.

My go-tos are;

Fruit, including just a handful of small tomatoes.

Nuts.

Celery and hummus.

Carrots with a peanut butter, soy sauce, lemon & chilli dip.

dates or other dried fruits and nuts

falafels and hummus - in pita with cut veggies

dolma - stuffed grape leaves (I buy them from a Middle Eastern store)

toasted Greek pita with a little olive oil rubbed on the top, zaatar spice, and pomegranate molasses (you can make any kind of quick pizza-like thing using flat bread/pita with your favorite toppings)

green smoothie (with ginger and mint)

Salad: Greens with cherry tomatoes, cucumbers, olives, lemon juice and hummus.

Thinly sliced sweet potatoes and white courgette with chili dipping sauce and hummus.

Nut guacomole: avocado, lemon, paprika / chili powder and pistachios or sunflower / pumpkin seeds.

Avocado is another go to - slice it in half, take out the pit and fill the center with soy sauce or lemon, salt, and pepper