Well I'd test that out first- & by all means take the temperature of the water that you put in the bottle. Don't overheat- don't overwhelm your snake in a confined space, as that can kill them- when they have no room to get away from excessive heat. That's why I prefer to transport snakes in a larger "ice chest"- the snake shouldn't be right next to a heat source, & unable to get away, as when they're stuck in a bag.
If you do use a thermal bag, where the snake is very close to a warm bottle, it needs to be wrapped for protection of the snake & the water should only be about 84* at most. See what I'm saying? I'll never forget- years back a guy on another snake forum had his favorite snake in a bag on the floor of his truck for transport- it was a several hours drive, & he never stopped to check on the snake- it died, because it got too warm & couldn't escape (thermoregulate properly).
Even if a snake doesn't die, being excessively warm can cause irreversible nerve damage in snakes. Better for a snake to be too cool than too hot.
okay perfect i will use the thermal bag but leave it open a bit for air flow and get a little bit hotter then lukewarm bottle wrap it in platic wrap. like i mentioned it is 5-6min walk so i will be there in no time i was more worried about the sudden shock of cold