1 large can pineapple juice
2 cups Tang instant drink powder
3 quarts water
Mix all together in a 5 - 6 quart container (the large plastic ice cream buckets work well - I don't think a gallon would be large enough though). Place in freezer. Take out and stir well every hour or so. When slushy serve in cups - kids love it!
If left in the freezer too long it will freeze into a huge popsicle. You can still serve it but scraping - but I hate that so I make the kids (most are in their 20's now) scrap it themselves.
If you have an ice shaver you could also freeze some in the smaller containers and shave it to make a flavored snow cone.