[Ethereum] “cancel” a token transfer transaction by sending ether

You can manually encode data with the function:

public static String encodeTransferData(String toAddress, BigInteger sum) {
    Function function = new Function(
            "transfer",  // function we're calling
            Arrays.asList(new Address(toAddress), new Uint256(sum)),  // Parameters to pass as Solidity Types
            Arrays.asList(new org.web3j.abi.TypeReference<Bool>() {}));
    return FunctionEncoder.encode(function);
}

and call the contract this way:

public static void main(String[] args) throws Exception {
    Web3j web3 = Web3j.build(new HttpService()); // defaults to http://localhost:8545/    
    Credentials creds = WalletUtils.loadCredentials("password", "path/to/wallet");
    RawTransactionManager manager = new RawTransactionManager(web3, creds);
    String toAddress = "0x..."; // destination address
    String contractAddress = "0x...";
    BigInteger sum = BigInteger.valueOf(10000); // amount you want to send
    String data = encodeTransferData(toAddress, sum);
    BigInteger gasPrice = web3.ethGasPrice().send().getGasPrice();
    BigInteger gasLimit = BigInteger.valueOf(120000); // set gas limit here
    EthSendTransaction transaction = manager.sendTransaction(gasPrice, gasLimit, contractAddress, data, null);
}

I can't see what's wrong with the token contract.

Concerning the second one, you should do :

function sendTokens () public payable returns (uint)
    {
        AppleToken appleToken = AppleToken(tokenAddress);
        require(appleToken.transfer(msg.sender, 10));
        return appleToken.balanceOf(msg.sender);
    }

1. No need to declare the appleToken variable then set it, you can combine both.
2. Be sure that tokenAddress is the correct one.
3. Always use a require when doing token transfer! Do not think it works like the transfer method for ether, which handles failure and will throw for you.

EDIT :

I have tested the contracts and it works fine. I think you simply forgot to send tokens to the EquityInvestments contract, hence token balance of msg.sender staying at 0.