Do you know you can watch the replay of the game anytime you want? You can watch the opponent's elixir in the replay too. So if you think your opponent is cheating, you can always watch the replay of the match to verify
I don't think no such cheat is available with clash of clans. Have you seen people playing almost 15hrs a day or more. I have a friend who plays at the middle of the night and gets only a couple of hours of sleep.