I got this recipe from a magazine many years ago. The tubs of caramel sauce made for dipping your apples into are expensive (at least for this mom) and this was a homemade version. Our family loves it.
Combine sugar, sweetened condensed milk, and corn syrup and cook until sugar is thoroughly dissolved and cooked. Add water and cook until bubbly. Add butter and vanilla and cook 5 more minutes. Be careful not to burn the sugar.