Clinton's infrastructure plan says only that it will be paid for through "business tax reform." It does not detail the nature of the reforms that would pay for this spending. Similarly, Sanders does not yet have a specific individual and corporate tax proposal, but he has proposed a financial transaction tax and says he will close loopholes.
A strangely popular proposal would give companies a temporary tax holiday, letting corporations "repatriate" their money at an extremely low tax rate, thereby encouraging more corporate tax dodging in the future. You'd think that common sense and strong opposition would be enough to kill a bad policy. Not in Washington, D.C., apparently.