You can use draw_set_transform
(docs.godotengine.org/en/stable/classes/class_canvasitem.html#class-canvasitem-draw-set-transform).
Something like this should work.
var my_string = "Hello World"
var x = (360) / my_string.length()
for i in range(0, my_string.length()):
draw_set_transform(Vector2(0, 0), deg2rad(i * x - (my_string.length()/2*x)), Vector2(1,1))
draw_char(font, Vector2(0, -30), my_string[my_string.length()-i-1], "", Color(0, 0, 0)