From Asian supply shops you can often find small packets of powdered fruits. Check the packet but many are made from actual fruit!
I have seen Apple, Cherry, Coconut, Lime, Mango, Pomegranate, Strawberry etc.
Google for powdered fruit and you'll find a variety of online sources
My favourite is Lime powder (99% Lime, made in Malaysia)
Add Aloe Vera powder to make a thickened drink
Add Arrowroot or instant custard powder to make a cloudy "juice"
Add Ascorbic acid powder (Vit. C) as a preservative (be careful not to exceed RDI)
Add Citric acid to make it more citrus like
Add sugar (real or fake) to bulk it out so a simple measure (e.g. one tea spoon) makes a glass of drink
Experiment with the quantities, but you don't need much of anything to get an effective result