Jumping Jacks. Or if you are British, side straddle hops.
Cold water
Cold to warm
is not the same
they are exactly the same in every way except the warm ones move faster
Warm Water! when molecules inside of an object heat up, the molecules go faster! which will absorbe the food coloring faster.
conduction
Warm air and warm water. Cold air and cold water keep ice cooler longer.
Cold water freezes faster then warm water.
warm water will rust metal faster
Cold water
Find someone who has a cold and ask them to cough in your face.
cold water because it is closer to freezing point alredy when hot water has to be coled down.
Warm front
Cold to warm
submerge the bottle in cold water.
is not the same
The fastest way would be something like a portable water heater. Otherwise you can boil water over a fire or if you have a portable cooking grill you can warm it that way.