What do I do with the green cash I make at lemonade stand?

As Sunny renovated various areas, especially near the lemon stand and orchard, tasks will often require the green cash ($500-1000 at a time).

I have noticed, however, that rather than fill the orders of the customers at the stands, it is easier to just focus on reaching level 21 (usually by quickly merging lemons over and over to make the Level 9 cosmetic boxes that regularly releases 100 purple energy points). Then you will obtain the bulk of the cash along with the pond pieces.

As you do quests for the main story you will sometimes encounter quests that require green cash, rather than items from the merge board.