Mix all ingredients, put into a container (shallower the better), pop into freezer.
Check on it again and again for hours. Each time you check on it, give it a good stirring. This serves two purposes: gets the frozen outer part to the middle so it freezes faster, and fluffs it up so it doesn't turn into hard ice chunks.
You'll know when it's done because you'll be eating it. My boyfriend thinks it could use less pineapple, so experiment to get your own magical proportions.
I came up with this when I had gone to the corner store with an ice cream craving and desperately needed an alternative! Luckily they have a big canned section. Too bad I didn't quell my craving until the next day, but now I know better. ;)