Try
Wild Fermentation for a reference.
I used to make vinegar often when I was in restaurants, mostly various wine and berry vinegars. Now, I sometimes make pineapple or coconut vinegar or, for the former, sometimes simply flavor rice vinegar with pineapple trimmings. It depends on whether I have pineapples (I grow a few) available.
Recipe: Pineapple Vinegar
From Wild Fermentation by Sandor Ellix Katz
1/4 cup sugar
Peel of 1 pineapple and any attached bits of fruit
water
cheesecloth (or old T-shirt)
glass jar
Note: Unless it's coming from your mom's backyard, you probably want to go organic here. You want pineapple vinegar, not pineapple-doused-in-poison-and-food-grade-petroleum vinegar.
1. In a jar or bowl, dissolve the sugar in 1 quart of water. Coarsely chop and add the pineapple peel. Cover with cheesecloth to keep flies out, and leave to ferment at room temperature.
2. When you notice the liquid darkening, after about 1 week, strain out the pineapple peels and discard.
3. Ferment the liquid 2 to 3 weeks more, stirring or agitating periodically, and your pineapple vinegar is ready.
Another Note: I left the peels in for about three weeks and never "agitated" and it worked just fine.