Place one strawberry on each skewer and set aside.
In a cold saucepan, combine water, corn syrup, sugar, and cream of tartar. Stir to moisten the sugar.
Heat the mixture over medium-high heat, boiling until the sugar dissolves and it begins to bubble. Avoid stirring while boiling.
After 7 to 8 minutes of bubbling, the sugar coating should be ready. If using a candy thermometer, the syrup reaches the "hard crack" stage at 300°F. Alternatively, dip a stick into the syrup and then into ice water to check if it hardens.
Turn off the heat immediately.
Tilt the pan so the syrup pools to one side.
Dip and swirl a strawberry in the syrup to coat.
Quickly immerse the coated strawberry into ice water to set the candy and chill the fruit.
Continue with the remaining skewers until the candy or strawberries are used up.
Remove the strawberries from the ice bath and place them on a serving dish.
Notes
Most basic tanghulu recipes rely on just sugar and water, but that syrup can harden too quickly after a few dips. This version includes a touch of cream of tartar to stop large sugar crystals from forming, and a bit of corn syrup to keep the coating smooth and crystal-free. Thanks to these additions, you can skip the candy thermometer. Just wait until the syrup starts bubbling.
Make sure the strawberries are completely dry before dipping to help the sugar syrup stick properly and create a smooth, hard candy shell.