SphereCollider.radius

Description

The radius of the sphere measured in the object's local space.

The sphere radius will be scaled by the transform's scale.

using UnityEngine;

//Always attach a SphereCollider component to your GameObject
public class Example : MonoBehaviour
{
    //This declares your SphereCollider
    SphereCollider myCollider;

    void Start()
    {
        //Assigns the attached SphereCollider to myCollider
        myCollider = GetComponent<SphereCollider>();
    }

    void OnTriggerEnter(Collider other)
    {
        //This increases the Collider radius when the GameObject collides with a trigger Collider
        myCollider.radius += 2f;
    }
}