Give a few hours after or before insulin, in a different location. Many of the insulins we use should not be diluted, so you want the fluids deposited in a different spot.
If you can, warm them up a bit before giving (without needle on kit, 15-30 seconds in a microwave may work), and wrap kitty in a warm towel or blanket. Cold fluids may drop the itnernal temperature quickly and be uncomfortable.