Use a heated chicken waterer
Add a stock tank heater or de-icer
Place the waterer in a sheltered, insulated area
Use black rubber tubs to absorb heat from sunlight
Refill with warm water several times a day
Use multiple smaller waterers and rotate them
Keep the waterer off the ground on a platform
Wrap the waterer with insulation
Use a floating de-icer in larger containers
Check and break ice regularly
Move the waterer to a warmer location
Use nipple waterers with a heated supply line
Cover the waterer to reduce heat loss
Clean the waterer often to improve heater efficiency