CAD tip # 13906:

Or you can use the Equation Curve. From the mathematical definition of a spiral you can get an expression for the function 3D Sketch > Drawing > Equation Curve - e.g. for 2 turns, in the Cartesian system:

x(t)=t*sin(t)/2
y(t)=t*cos(t)/2
z(t)=0
t min: 0   t max: 720

An even simpler and more logical expression (equation) would be in Cylindrical space:

r(t)=t*0.25
θ(t)=t
z(t)=0
t min: 0ul   t max: 720ul