A couple of the keys on my MacBook Pro became sticky (drink fell on table and a few drops appear to have splashed onto top right of keyboard). If I bring my device to Genius Bar in store, will they likely take a couple minutes to clean it for free?

Apple doesn't clean liquid spills. Apple replaces any and all parts which show signs of liquid damage. For a keyboard, this entails replacing the entire Top Case Assembly which includes the Keyboard, Trackpad, Battery (and Touchbar & Speakers on some models). And yes, this is an expensive repair (easily $500+ US). If the liquid made it past the keyboard, then the Logic Board or other electronics may have been damaged as well. It doesn't matter if the laptop is otherwise working, if there is signs of liquid damage or a liquid sensor is tripped, Apple and the AASP will insist on replacing those parts due to Apple's rules for official repairs.

Maybe an Apple Authorized Service Provider would be willing to pop a few key caps off the keyboard to try cleaning them, but it would not be free and it risks breaking the key cap and scissor mechanism. FYI, if you have a 2016-2019 model with the Butterfly keyboard, then there is no way to clean them since the butterfly mechanism cannot be detached for cleaning.