When the Travel Jar is active, it'll collect coins for every level you complete! The more levels you play, the more coins it can earn.
Make sure to get those coins before time runs out! You'll see the timer located at the bottom of the screen when you select the Travel Jar icon.
To collect the coins from the jar, just select the jar icon and follow the instructions on the screen.
Keep in mind that the Travel Jar contents cannot be purchased if there are fewer than 300 coins inside.
The maximum coins the Travel Jar can hold is 600.