You will probably never eat a sloth. For one thing, they're paralyzingly adorable. Furthermore, for as sluggish as they are, sloths meat is — surprisingly — not very tender at all; in fact, it's reported to be pretty tough and gamey. Finally, it's illegal to hunt them — and most of the South American tribes that can get away with bending the law have some qualms about killing them, anyway.
Having said that, sloths do get eaten. According to this study [PDF], your typical South American tribesman eats 0.064 sloths annually. Ratcheting up that average substantially for all the other tribes that live within hunting-range of sloths are members of Brazil's Pirahã tribe. Slate's Brian Palmer spoke with anthropologist Daniel Everett — who has spent upwards of seven years living with the Pirahã — about the subtleties of sloth preparation:
If you somehow find yourself in possession of a sloth carcass and want to eat like a tribesman, preparation is simple. The Pirahã singe off the hair, gut the animal, and roast chunks of muscle over a fire. When the meat is thoroughly cooked, they tear off pieces with their hands and eat it plain. For the American palate, however, a little culinary doctoring can go a long way. Everett prefers to tenderize the meat in a pressure cooker for 40 minutes, season it with cilantro, garlic, salt, and chili sauce, and add it to tacos.
"But for the record," Everett explained, "spices may do wonders for the palatability of sloth meat, but they'll do almost nothing to help fill the gaping void that devouring a sloth leaves in your soul."