I've had parents send in apple slices for snack and an alternative to lemon juice is orange juice. One time the kids gobbled up some apple slices and I was telling the Mom and she said it was probably because she dipped them in 7up! Sounds strange but they looked crisp, too!
Fruit Fresh. It's a powder and it comes in a shaker can-look by canning stuff in the store next time you're shopping-won't help for tomorrows lunch though. My friend uses pineapple juice when making fruit salads-don't know if that'll help the salad situation either.