To distinguish the authenticity of the Anta swimming cap on Pinduoduo, you can try the following methods:

1. Merchant reputation and evaluation: When purchasing goods on Pinduoduo, you can Check the merchant's reputation and reviews. If the merchant has a good reputation and has many positive reviews, then it is more likely to be genuine. And if the merchant has a poor reputation and has many negative reviews, it may be a fake.

2. Product price: Although there will be some discounts and promotions on Pinduoduo, if the price of a product is significantly lower than the market price, it may be a warning sign. If the price is too low, it is likely to be a fake.

3. Product pictures: Check the product pictures carefully and compare them with the product pictures on official channels. Pay attention to compare the product details, trademarks, logos, packaging, etc. If there are obvious differences with the official pictures, it may be a fake.

4. Product description and details: Read the product description and details carefully to see if there are any suspected errors or incomplete information. Authentic products will usually provide detailed product descriptions and specifications, while fake products may have missing or incorrect descriptions.

5. Consult customer service or the Pinduoduo platform: If you still have questions about the authenticity of the product, you can consult the Pinduoduo platform or contact the official customer service of the product. They can provide more help and confirmation.

Finally, if you find that the goods you purchased are fake during the purchase process, you can promptly complain to the Pinduoduo platform and seek a refund or exchange solution. In short, to ensure that you purchase genuine ANTA swimming caps, it is recommended to choose a reputable merchant and verify the authenticity and quality of the product in multiple ways.