Sandy Shocks's best moveset in Pokémon GO is Splash and Struggle, with 12.25 damage per second, and it can deal 380.3 damage before Sandy Shocks faints. This is true when battling in neutral weather.
All Sandy Shocks movesets ranked
Here is a complete list of Sandy Shocks movesets in Pokémon GO, ranked by their DPS and TDO. You can change the weather and the opposing Pokémon.