Update a product custom field

import { createAdminClient } from '@spree/admin-sdk'

const client = createAdminClient({
  baseUrl: 'https://your-store.com',
  secretKey: 'sk_xxx',
})

const customField = await client.products.customFields.update('prod_UkLWZg9DAJ', 'cf_AbC123XyZ', {
  value: 'cotton',
})

spree api patch /products/{product_id}/custom_fields/{id} -d '{"value":"cotton"}'

{
  "id": "cf_UkLWZg9DAJ",
  "label": "Title",
  "type": "Spree::Metafields::ShortText",
  "field_type": "short_text",
  "key": "custom.title",
  "value": "cotton",
  "created_at": "2026-07-26T14:25:35.308Z",
  "updated_at": "2026-07-26T14:25:35.590Z",
  "storefront_visible": true,
  "custom_field_definition_id": "cfdef_UkLWZg9DAJ"
}