1. Extras
2. redeem code: GetInline
3. enter and okay to get 150 sardines (the store currency)
4. options (gear top left)
5. more options >
6. erase game data
7. yes and then hold to confirm
8. Repeat steps 1 through 7 over and over till you have enough sardines to buy your way through the entire game. Store purchases and sardines transfer through saves.

Do this until you can buy everything in the black market and then save up an additional 11,256 (Yes I did the math and that's a rough idea of what I got, maybe save up a little bit more to be safe) This will be enough for you to get max level +100 on all bonuses and max level +7 for all gold bonuses in the bonus shop.

Link to the youtube video that showed me this was possible:
https://www.youtube.com/watch?v=P7_RQas0IbY&t=66s


To complete this all you gotta do is complete days and then on the ship upgrades screen a baby penguin will randomly pop up at either 4 sides of your screen which you click to get a youtube link. I recommend doing this in a save game with 0 upgrades on your penguin and using the fast forward ability from the black market to complete days quickly.