You can see all the things that worked for my bunnies as wells as for a few other members in our Cooling Tips section
I also have a new tip that I have yet to add to that section. I found that if you wrap water bottles (large or small) in a towel, they stay cool longer, and as the bottle sweats or if it leaks, the towel comes in handy, and it also prevents your bunny from chewing on the bottle, however, if your bunny likes to chew on towels and blankets…well, then this may not work for you.
I get the extra large bottles and make little bed sides out of them. i also paired that up with large ceramic tile squares that stay cool (if you have hard wood floors, put something soft underneath the tile otherwise you can scratch the floor over time 
So here are a few pics. Jack goes back and forth between the tile and the cool bed (though he prefers hanging on tile) while Vivian sticks to the “cool” beds only. In the last pic, Jack chose to stay in his hideybox where there is a frozen water bottle and tile too.


