Using 5.9 pb−1 of e+e− annihilation data collected at center-of-mass energies from 3.640 to 3.701 GeV with the BESIII detector at the BEPCII Collider, we measure the observed cross sections of e+e−→KS0X (where X=anything). From a fit to these observed cross sections with the sum of continuum and ψ(3686) and J/ψ Breit-Wigner functions and considering initial state radiation and the BEPCII beam energy spread, we obtain for the first time the product of ψ(3686) leptonic width and inclusive decay branching fraction Γψ(3686)eeB(ψ(3686)→KS0X)=(373.8±6.7±20.0) eV, and assuming Γψ(3686)ee is (2.33±0.04) keV from PDG value, we measure B(ψ(3686)→KS0X)=(16.04±0.29±0.90)%, where the first uncertainty is statistical and the second is systematic. © 2021 The Author(s)