WTF . Really nothing at all.
Just take a look at other games .
Here’s some examples from only one game I am not gonna name it
1 - free energy for 48h
2- a special weapons (like the highest lvl weapons you can get )
3 - enough items to do a 45 pulls in a wheel for the promo toons
4- world map drops Gold ,a pretty good amount comparing to normal days
And more , every 1 or two hours a free offer pop up and trust me all free pffer are worth 4-100 $ in normal days