The daily snack is a push notification Tapas sends out daily around noon your local time zone. It features 5 to 6 episodes, usually many of them premium series to help boost key sales.
At one time we were actually keeping records on what free series were getting featured in the daily snack. After we voiced some concerns that the same series were being featured too often (e.g. GamerCat received 5 daily snacks in two months) staff made a more conscious effort to try to feature things that have never been before including B&Ws, long form, and non gag-a-day.
There is no way to submit yourself for the snack. You have to be noticed by staff and they decide whether or not put you in. In the past, we've tried nominating other series by creators we like, with little success.
Ultimately after about 13-14 months since joining Tapas, and raising concerns about repeated series, we received our first snack (nominated by an intern! Thank you intern!). We incorrectly thought that it would create a huge following for our series. The impact was not as meaningful as we had hoped. The snack only generated 14k views with the vast majority of the readers reading only the one featured episode and nothing else in the series. It also generated 921 subscriptions, many of which dropped off in future updates.
At the end of the day, while a snack is nice, it's not a cure all for a series that is having a hard time gaining a following. We've had three snacks to date, two spotlights, and we're standing at just over 7,200 followers.
As @Elgenar points out, a lot of people are skipping past the Tapas homepage, so spotlights don't have the same impact that they used to. We jump right to the creator dashboard so we're just as guilty.
Tapas reports approximately 2M monthly users. SimiliarWeb reports approximately 10M website visits. So this means that the average desktop Tapas user is only visiting about once per week. A spotlight only runs for three days and a snack for one day. This is why they aren't having the sort of positive impact that you would expect it would.
We wouldn't get too excited about trying to chase down a daily snack feature. It's just not worth the anguish.
The snack is largely ignored by many. The app boasts 75,000 daily users, but on our first snack we only received 14,000 views for the entire series. This indicates that there is a very low read thru rate on the snack. When was the last time you looked at the snack? We haven't for months because it's just not relevant content. Since we don't read romance, which makes much of the snack non applicable to us. We have a feeling that many others feel the same way. Staff should consider looking into letting readers set content preferences to make finding things easier and the daily snack more meaningful to the individual. This would most likely dramatically increase the read thru rates. Unfortunately this would require a massive amount of coding and we're not anticipating this happening any time soon.
As @ilustrariane points out, the few times we've looked the snack the last few months, the content appears to be highly repetitive. We stopped keeping snack records in 2017 so there's no way to quantitatively confirm this, it is merely an observation.
In our experience the best way to increase views is to look into running ads for your series. TopWebComics offers a $1/day sponsorship which is hands down the best $1 you can spend on ads anywhere. Google AdWords does cost slightly less per click, but the time investment to learn and use the system makes it where you need to have a large spend to make it worth the extra effort.
Hopefully in the future we can share some way to rapidly increase series growth, but right now it remains a very allusive creature.