Toddler loves to spill milk

My son has started 2 new bad habits that I’m unsure how to resolve. The first is he takes his sippy cup, and puts it upside down, then bounces it on the floor to spill the milk.

The second is he will drink some milk, or rather fill his mouth with milk, then leave it open to let it fall out of his mouth onto the floor.

Both are, I think, to get the dogs to drink the milk, and therefor get close to him.

I’m not sure how to stop this behavior. I’ve tried timeout, but I don’t think it’s doing anything at this age.