I am always spilling drinks on mine, orange juice, coffee and even wine. My letters also kept getting stuck but I didn't want to buy another keyboard as the very cheap ones sold for between £5 and £10 do not have a calculator button and it is something I use often.
I tried all sorts of ways to clean it ie vacuuming, using wet ones and using a fine paint brush. A couple of letters were still sticking so I took it all apart. It was a bit of a jigsaw puzzle putting the keys back in again but after a thorough cleaning it worked. I realised that I might have been doing more harm than good but I considered it a write off how it was so had nothing to use. That was three months ago and it has been working perfectly ever since.
Be careful if you take it apart so as not to disturb too many of the keys.