Konpeitō, but only on rare occasions because it's impossible to find.
...You know, the candy that Starbits from Mario Galaxy were inspired from?
I only ever remember eating them to power me through Splat 1's earlier Splatfests because they were fun at the start, but the rate at which you got points before Splatfest Power was added was pitiful, and it usually took a solid... 4 hours of straight Splatooning I think to get to the top rank. Now you can get to the max rank in half the time so I'm saving my solid sugar candy for something else instead.