Last time I put the mulberries in muffins, along with the dregs of a bag of mixed berries; pretty good! The mulberries don't add a lot of flavour, but they do contribute a nice crunch and some sweetness to back up the other berries. (The tree near me makes regular purple/black ones, though; I don't know if the flavour is different with the white ones or not.)

Pepper flakes shouldn't dissolve, but the heat should leach out of them pretty well; that's basically what happens when you put them in food, so. :D I don't think oil would work, because it would keep separating from the water (or, if you just put the oil mixture in the bottle, it might be too thick to go through the spray nozzle, and/or glob up on the leaves) but it might be worth a try if you already have some. Maybe pepper-water on the leaves, and pepper-oil on the fruit? It might stick better to the rounded shape of a tomato than water would...