Chilis and peppers are something that wild turkeys eat often when they are available. The capsaicin in the seeds of the peppers are what deworms your birds. It also helps kill off any of those pesky little worms inside your birds' bellies. Any pepper with a high amount of capsaicin in the seeds will work.
So, if you had to choose between some, I'd recommend some hot ones like jalapenos. They are decently spicy and pretty inexpensive. You can used jarred peppers, but some people just prefer to buy the dry ones because they store well and don't involve a lot of fishing them out. Cayenne powder works, too, but sometimes it can get a bit pricy to keep buying the powder. If you have a Latin food market around where you live, you can buy loads of dried peppers for your birds and it won't cost very much. I live in Deep South Texas, so we have what we need at WalMart or HEB.
You can mix garlic and peppers into your turkeys' water. Though, if you don't mind me asking, what is the garlic for? I've never heard of someone putting it in their turkeys' water.