Pour water and sugar into a LARGE bowl and stir until sugar is completely dissolved.
Add pineapple, orange and lemon juice. Mix well.
Pour into large freezer safe Tupperware. I can get mine into 2 large tupperwares. Freeze until set.
Using an ice cream scoop, scrape mixture to create slush. Once you have created the amount of slush you want to use, mix it with half and half proportions with 7-up.
If I am only making this for my little family, I only scrape out enough for what I want to drink at the time then put the rest back in the freezer to use again later.