There are several ways to do digital marketing without spending money. Here are a few options:

1. Social media marketing: You can use social media platforms like Facebook, Instagram, and Twitter to promote your business or product for free. This can be done by creating a business account and posting regular updates, as well as engaging with your followers.

2. Content marketing: You can create and share valuable, relevant, and consistent content to attract and retain a clearly defined audience. This can be done through a blog, social media posts, or email newsletters.

3. Search engine optimization (SEO): You can optimize your website and its content to rank higher in search engine results pages, which can bring more organic traffic to your site. This can be done through keyword research, optimizing page titles and meta descriptions, and creating high-quality content.

4. Influencer marketing: You can reach out to influencers in your industry and ask them to promote your product or service in exchange for a free sample or other incentive.

5. Email marketing: You can build an email list and send newsletters or promotional emails to your subscribers. There are several free email marketing tools available, such as Mailchimp and Constant Contact.

It's important to note that while these methods can be effective, they may require time and effort to produce results.