Fridays are my favorite - we do a "mystery" snack shack in the form of either a treasure map to follow (that leads to the snack) or a clue (or series of clues) they have to solve to find their snack. Usually this leads them to places like the garage fridge where there are ice cream sundaes waiting for them, or upstairs to the playroom where there is a snack picnic laid out (they love bowls of yogurt with "treats" they can put in (M&Ms, chocolate chips, granola, whatever):
Now don't get me wrong, not every day is this exciting - yesterday I was running REALLY short on time and I simply laid out an arrow of butter knives pointing directly to the fridge (where they could simply pick out whatever they wanted from the snack bin, lol) - not exactly labor-intensive, but it was still fun for them nonetheless.
My [ahem, professional] snack suggestion: make a list of easy snacks your kids like and jot them down (peanut butter crackers, veggies and hummus, chips and dip, etc) - that way when you're short on time, you can think of something quickly - and, if you really want to make their day, draw a few arrows on a post-it note and your kiddos will think you are a snack hero (yes, even when there's just a yogurt cup waiting for them on the other end). :)