How to render procedurally generated mesh to be rendered as 2 sided?

You would need to use a custom shader. The following shader will work, although it is a simplified version of the Standard shader because I don't know what shader you would otherwise be using/what features.

 // Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
 
 Shader "Custom/Double Sided"
 {
     Properties
     {
         _Color ("Main Color", Color) = (1,1,1,1)
         _MainTex ("Texture", 2D) = "white" {}
         _Smoothness ("Smoothness", Range(0,1)) = 0.5
         _Metallic ("Metallic", Range(0,1)) = 0
     }
     SubShader
     {
         Tags { "RenderType"="Opaque" }
         
         Cull Off
         
         CGPROGRAM
         #pragma surface surf Standard vertex:vert
         #pragma target 3.0
         
         sampler2D _MainTex;
         half _Smoothness;
         half _Metallic;
         fixed4 _Color;
         
         struct Input {
             float2 uv_MainTex;
         };
         
         void vert (inout appdata_full v) {
             float3 worldPos = mul (unity_ObjectToWorld, v.vertex);
             float3 worldNorm = UnityObjectToWorldNormal (v.normal);
             float3 viewDir = worldPos - _WorldSpaceCameraPos;
             v.normal *= dot (viewDir, worldNorm) > 0 ? -1 : 1;
         }
         
         void surf (Input IN, inout SurfaceOutputStandard o) {
             half4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
             o.Smoothness = _Smoothness;
             o.Metallic = _Metallic;
             o.Albedo = c.rgb;
             o.Alpha = c.a;
         }
         ENDCG
     }
 }