spilled cola stuck/sticky buttons

soo yesterday I spilled cola over my iphone 5 it has a screen protector and a case and I could easily wipe all the cola off the screen but some of it got into the volume buttons and silent switch they still function correctly except that it is really hard to press them it requires a lot more force and I don't want to break anything

I'm afraid that unscrewing my iphone to clean it voids my warranty but I don't know another way to clean it

so does anyone know a way to clean it?