Maybe a little squeaky baseball (Jake loves his), bubbles are a great idea as mentioned above
, a water bottle that can be taken on walks, doggie baseball cap, wipes to wash them with and cool them off, a cooling collar. Maybe a couple pieces of fruit with a recipe for making frozen dog ice cubes out of it, pet sunblock. A couple bully sticks or flossies, of course.
Here's a link with some really cute summer dog toys.
http://www.funstufffordogs.com/Qstor...76712347&BACK=