Rewarded Interstitial is a full-screen, non-skippable ad that can be closed after 15 seconds by clicking on the cross icon. You should reward a user for watching an ad to the end. Looks like a telegram post:
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Inside the Telegram Mini App, it will look like this:
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For advertising to bring you money and not create negative emotions in users, it has to be:

There are several types of rewards you can use. You can create any reward that works for your app. The types below are just examples.

Boosters. Give users some boosters, such as a mining multiplier or a speed multiplier, reduce downtime, use an existing booster in your game, or create a new one.

One more chance. When players lose in the game, they have the option to obtain an ability that will allow them to continue playing.

Use ads as a currency. If the user does not have enough in-game currency, offer to show ads and add the missing amount of in-game currency.

Earn page. Many applications have a separate page for earning in-game currency, you can add it there along with other tasks.

Any reward suitable for your App. The above examples are not the only ones that are possible. There may be a more appropriate place for advertising in your mini app.

The detailed manual on how to integrate a Rewarded Interstitial into your app can be found in this article.
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More examples of the Rewarded interstitial usage may be found in the Code Examples article.
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