1 (46 oz.) can unsweetened pineapple juice
2 1/4 c. orange juice
1/4 c. lemon juice
4 c. water
2 c. sugar
Ginger ale

Bring water and sugar to a boil. Add juices. Freeze 12-24 hours, stirring occasionally while it is freezing. When ready to serve, put some of the slush in a tall glass and pour ginger ale over it.