It starts by firing bursts at the ground in random spots, then doing the same against the ceiling. After it does these attacks, it will angrily fire a barrage of shots all over the ground area. It will then repeat it's chain of attacks.
There is a hover booster that can be used to access a rail above Sparky that can be used to attack it.
While playing as Milla, she can find and ride Sparky in the fifth area of Battle Glacier until the fight against Dail and the Shade Beast. It has a green and orange color scheme, and an eye similar to Milla's. Warning: shooting upwards while riding on Sparky will damage Milla.