What a little cutie! Congratulations! I'm sorry it's so hot in your apt. and the AC is broke. I would refrigerate his water and add ice cubes to it. I give mine distilled water, as my vet told me it's better for their eyes. I have to refrigerate it because my little guy likes his water COLD.
I think there are puppy cooling pads that you can buy for them to lay on. You might want to google it and see what you come up with. You could also give him a bath to cool him off if he seems overheated. I'm sure the vet will be able to give you advice too.