he easiest way to handle the bacon situation is to remove it from the package and while it's still all stuck together, stretch it out a little (lengthwise). If you're using center-cut bacon (and the "slab" is not as wide as regular bacon), just cut it in half. Otherwise, use kitchen shears to cut the slab into thirds. Refrigerate until ready to use, partially because it's easier to work with cold bacon and partially because you don't want to kill any dinner guests with dead pig germs.
Using kitchen shears, cut chicken into bite-sized pieces. You can gauge about how many pieces you'll need by how many pieces of bacon you have; you probably won't use all the bacon, but you'll need about 8 oz. or 2/3 of a standard-sized package of bacon. So count the bacon pieces and keep that in mind when cutting up your chicken.
Drain the pineapple and set up a little work station with skewers, bacon, chicken, and a 9x13 baking dish (for big skewers) or a sturdy Ziploc bag (for toothpick skewers). Wrap a piece of bacon around a chicken piece, secure with toothpick/skewer, and top with a chunk of pineapple. Repeat twice if using large skewers.
When all chicken pieces have been sufficiently staked, pour Teriyaki sauce over everything, reserving about 1/4 c., and marinate in refrigerator for at least 4 hours, no longer than about 8.
Preheat grill; when about 350-400 degrees, place skewers on grill and baste with reserved Teriyaki sauce. Cook about 7 minutes and flip skewers. Baste again and cook another 7 minutes.