Not sure if serious, but consider English "to", "too", and "two".

Disclaimer/explanation: I actually studied Japanese, but I'm assuming the same principle applies. If so, the symbols would be different because of the differing meanings, and the pronunciation is coincidental.

可 means "able to" (so 可口 could be sort of literally translated as "mouth-able"), whereas 渴 actually means thirsty ("mouth thirsty").