How to fix warning messages in the SDTT if the data is not available?

Question

One of my client is e-commerce marketplace. For their offer listing pages, I have provided a JSON structured data Product markup using aggregateRating as follows:

<script type="application/ld+json">
{
  "@context": "https://schema.org/",
  "@type": "Product",
  "name": "example name", 
  "description": "example description",
  "aggregateRating": {
    "@type": "AggregateRating",
    "ratingValue": "4.7", 
    "ratingCount": "20",
    "bestRating": "5",
    "worstRating": "1"
  }
}
</script>

So far everything is good. Everything works fine; and the structured data is displayed properly on Google SERP.

Issue

Although, there are 6 warning; as the markup is for Product. Here is the screenshot:

Warning are for the following six fields:

• brand,
• image,
• offers,
• review,
• sku
• unique identifier (either of isbn, mpn or gtin8)

There are 0 Pages with Errors, 40 Pages with Warnings and 0 Valid pages in Google Search Console. They recommend to fix these warnings so that it can be considered as a valid markup. Here is the screenshot:

I do not have SKU and unique identifier, so how can I fix these warnings? I did research on Google Documentations and Schema.org but there is no other way to fix these errors than to provide all these values.

I have a doubt that Google may penalize in future because of these warnings. Is there any way I can by-pass these errors or do tweak in code?

Update 1

Google keeps on sending notification about these warnings. Google suggests to fix them ASAP. Thing is, I do not have these values on the page. So is there any way to tell Google that these values do not exist on the page? For example can I add in structured data code something like

• "brand": "Not Applicable";
• "image": "Not Applicable";
• "offers": "Not Applicable";
• "review": "Not Applicable";
• "sku": "Not Applicable";
• "gtin8": "Not Applicable".

Update 2

I received below message on these warnings. This clearly stats that

Search Console has identified that your site is affected by 6 new Products related issues. This means that Products may be negatively affected in Google Search results. We encourage you to fix these issues.

Answer 1

I do not have SKU and unique identifier, so how can I fix these warnings?

Is there any way I can by-pass these errors or do tweak in code?

There is no way to fix this other than to provide the data.

I have a doubt that Google may penalize in future because of these warnings.

As long as it’s just a warning, you can still get the search result feature ("Please provide a value if available."). Depending on the missing data, the search result feature might miss some features.

If it’s an error, you can’t get the search result feature.

No matter how many warnings/errors the SDTT shows, your page won’t get penalized (unless you try to deceive). The only drawback is that the result for your page doesn’t get the search result feature.

Answer 2

As you can see those warnings are recommendation not mandatory. Google is suggesting you to add those information.

One of my client is e-commerce marketplace. For their offer listing pages, I have provided a JSON structured data Product markup using aggregateRating as follows:

As you said you're creating schema for offer, your JSON is not correct, you should go through - https://schema.org/Offer, you can also add offer type in your product.