Distilled or Deionized water only, don’t use bottled ot tap water, it can cause mineral deposits and clog up the radiator and inlet. You can use a little water wetter, since we are in FL I don’t use coolant. There is no need.
Check your tracks regulations on this. Many will require water only and ban any additives like water wetter or antifreeze. Like Sahib said, distilled water only or you get mineral deposits. Ask me how I know!
As above, distilled water only. Normal water is fine but can leave deposits as noted.
Most places specifically ban coolant because a coolant leak is a disaster to clean up.
Water. Add vinegar for the last session of the year to get rid of any scale and then drain it to stop it from corroding the aluminum.