I just pulled out Appletun like I did for the previous run of this event.

Appletun w/Terrain Extender
Ability: Thick Fat
Modest Nature

252 HP EVs
252 Sp Atk EVs
4 Def EVs

• Apple Acid

• Grassy Terrain

• Iron Defense

• Giga Drain

Start of with grassy terrain. Then spam apple acid until you can tera then tera grass giga drain. It is honestly a pretty easy build and there is a very low chance of you going down with grassy terrain and giga drain.