Inkay evolves by giving it the item obtained by winning 5 challenges in the 3-1 zone.
There are ways to farm a lot of money without being at the computer, for example at night, by activating the repeat option.
After completing all 100 waves of a map, its challenges are unlocked. (If you've downloaded the game)
In a challenge egg
Is there an alternate way to evolve Inkay? Because I quickly leveled him up to 100 and then realized he didn't evolve...