If this is the SB keyboard, then, there is no hope.
But if it is the thin detachable keyboard, you may be able to save it.
The sugars and other acids in Coke are particularly troublesome.
As long as you accept that your keyboard is already ruined, you can try this, because it MAY help:
Prepare a bath of warm water with a very tiny bit of liquid soap (not shampoo) added. Dunk the keyboard face up a few times then invert it and tap it on the back to try to let it drain. Repeat all of this a couple more times.
Then use a hair dryer (not too close) to blow warm air through the inverted keys to dry it out.
Do not connect it to your Surface until it is dry.