This week it's been fresh apricots according to MFP they're under 20 cals (depending on weight)
Or rhubarb stewed with ginger and a bit of sweetener around 20 cals for 100g.
Light babybels are 42 cals if I'm feeling cheesy.
Nestle kvarg is around 80 cals a pot and high In protein so fills me up for a while.