Sky Drop is learned by 4 species by level and 22 by machine

Effect, in PokéAPI's words

“Carries the target high into the air, dodging all attacks against either, and drops it next turn.”

Who learns it

22 species in all, 6 games

Ultra Sun and Ultra Moon: 22 species

Species	Method	Level
Aerodactyl	Level up, Machine	49
Rufflet	Level up, Machine	50
Braviary	Level up, Machine	50
Hawlucha	Level up, Machine	55
Charizard	Machine
Articuno	Machine
Zapdos	Machine
Moltres	Machine
Dragonite	Machine
Mew	Machine
Skarmory	Machine
Lugia	Machine
Ho-Oh	Machine
Pelipper	Machine
Rayquaza	Machine
Tornadus	Machine
Thundurus	Machine
Yveltal	Machine
Vikavolt	Machine
Tapu Koko	Machine
Lunala	Machine
Naganadel	Machine

Sun and Moon: 21 species

Species	Method	Level
Aerodactyl	Level up, Machine	49
Rufflet	Level up, Machine	50
Braviary	Level up, Machine	50
Hawlucha	Level up, Machine	55
Charizard	Machine
Articuno	Machine
Zapdos	Machine
Moltres	Machine
Dragonite	Machine
Mew	Machine
Skarmory	Machine
Lugia	Machine
Ho-Oh	Machine
Pelipper	Machine
Rayquaza	Machine
Tornadus	Machine
Thundurus	Machine
Yveltal	Machine
Vikavolt	Machine
Tapu Koko	Machine
Lunala	Machine

Omega Ruby and Alpha Sapphire: 18 species

Species	Method	Level
Aerodactyl	Level up, Machine	49
Rufflet	Level up, Machine	50
Braviary	Level up, Machine	50
Hawlucha	Level up, Machine	55
Charizard	Machine
Articuno	Machine
Zapdos	Machine
Moltres	Machine
Dragonite	Machine
Mew	Machine
Skarmory	Machine
Lugia	Machine
Ho-Oh	Machine
Pelipper	Machine
Rayquaza	Machine
Tornadus	Machine
Thundurus	Machine
Yveltal	Machine

X and Y: 18 species

Species	Method	Level
Aerodactyl	Level up, Machine	49
Rufflet	Level up, Machine	50
Braviary	Level up, Machine	50
Hawlucha	Level up, Machine	55
Charizard	Machine
Articuno	Machine
Zapdos	Machine
Moltres	Machine
Dragonite	Machine
Mew	Machine
Skarmory	Machine
Lugia	Machine
Ho-Oh	Machine
Pelipper	Machine
Rayquaza	Machine
Tornadus	Machine
Thundurus	Machine
Yveltal	Machine

Black 2 and White 2: 16 species

Species	Method	Level
Aerodactyl	Level up, Machine	49
Rufflet	Level up, Machine	50
Braviary	Level up, Machine	50
Charizard	Machine
Articuno	Machine
Zapdos	Machine
Moltres	Machine
Dragonite	Machine
Mew	Machine
Skarmory	Machine
Lugia	Machine
Ho-Oh	Machine
Pelipper	Machine
Rayquaza	Machine
Tornadus	Machine
Thundurus	Machine

Black and White: 16 species

Species	Method	Level
Aerodactyl	Level up, Machine	49
Rufflet	Level up, Machine	50
Braviary	Level up, Machine	50
Charizard	Machine
Articuno	Machine
Zapdos	Machine
Moltres	Machine
Dragonite	Machine
Mew	Machine
Skarmory	Machine
Lugia	Machine
Ho-Oh	Machine
Pelipper	Machine
Rayquaza	Machine
Tornadus	Machine
Thundurus	Machine