>>42163038>>42163116From Slowpoke's dex entry (Silver and SoulSilver):
"A sweet sap leaks from its tail's tip. Although not nutritious, the tail is pleasant to chew on."
Seems like it's only used as bait and for home cooking (Moon and UltraMoon entry):
"Alolan home cooking involves drying Slowpoke tails and then simmering them into a salty stew. "
"Although their tails, which fall off naturally, can easily be found lying around, they're a precious ingredient for cooking."
https://bulbapedia.bulbagarden.net/wiki/Slowpoke_%28Pok%C3%A9mon%29 
