What do y’all do for your active dogs during the day?

My father recently got sick and in the meantime I'm taking care of his dog for him. Since it's hotter than satan's ballsack I'm not really sure what we can do. I walk him early in the morning before the sun rises, but those only take him out for about half the day, then he's back up and going crazy. He's a nearly solid black shepherd and just not really meant for the sun, I tried taking him to a dog park that's all grass and water and he spent most of the time laying down in the shallows and looking at me like I was stupid. What indoor activities work for those of you with active/working dogs?