In addition to purchasing Ink in the Ink Shop, Tapas offers a variety of ways to earn Free Ink by completing special offers sponsored by various partners.
These usually appear in the Free Ink section of the Android and iOS app, but in some cases may appear after the episodes of a particular series or be announced in a popup or inbox message.
The number and variety of Free Ink opportunities available to you will vary based on your location and other criteria set by the advertisers sponsoring the offers, and may include watching video ads, playing game demos, taking surveys, downloading other apps, and more.
The requirements for special offers involving other apps may be as simple as installing the app or game via the button or banner in Tapas, while in other cases you may also need to then reach a specific level or perform certain other tasks to earn the reward.
The details for each special offer are different, so make sure you've followed the instructions carefully and have completed all of the requirements to claim your reward.