Contact your vet to determine if any other measures need to be taken. For example, if your bunny is severely dehydrated, he may need fluid replacement. Prevention of Heat Stroke Water. Even in winter rabbits must always have fresh water to drink. In the summer time, water is even more critical.
Every bunny loves ice cubes in the water.
This is a good time to give the bunny an extra water bottle. It's also not a bad idea to place a bowl of ice in his cage in the morning or early afternoon. As the ice melts, the bunny will have fresh cold water available. If your bunny is outdoors, he needs lots of shade. Made sure he has a shelter in his cage where he can escape the sun.