Hi,

Create a Computed Field for SKU:

First, create a computed field in your product template or product variant model that will calculate the SKU based on the selected variant.

from odoo import fields, models, api

class ProductTemplate(models.Model):

    _inherit = 'product.template'

    variant_sku = fields.Char(string='Variant SKU', compute='_compute_variant_sku', store=True)

    @api.depends('product_variant_ids')

    def _compute_variant_sku(self):

        for template in self:

            if template.product_variant_ids:

                template.variant_sku = template.product_variant_ids[0].sku

            else:

                template.variant_sku = ''

class ProductProduct(models.Model):

    _inherit = 'product.product'

    sku = fields.Char(string='SKU')

    @api.onchange('sku')

    def _onchange_sku(self):

        for variant in self.product_tmpl_id.product_variant_ids:

            variant.sku = self.sku

sku in ProductProduct is the field where you enter the SKU for each variant.

Hope it helps