Grapes, strawberries, pineapple, melon, all syn free! You could bring one of those little fruit salad boxes?
Velvet crunch 4 syns a bag, rainbow drops 28g = 4 syns, skips 17g bag 4 1/2 syns, skips 15.5g bag 4 syns, all I can think of right now.

Oh and rich tea finger biscuits only 1 syn a biscuit!