This, of course, should only be done when there is no harm that can come to your child or anyone else. For example, if your child is in the habit of throwing their juice when in their high chair, let them throw the cup.  Before handing them the cup, remind them of the rule and the consequences: "Remember, if you throw your cup, your juice will spill and you won't have any juice to drink." A mess on the floor might be annoying for you, but there's a good chance you'll need to clean the floor after a 2 year old's meal anyway. After they throw their cup on the floor, the 2 year old will undoubtedly ask for their juice. Point out that since they threw the juice, there is no more juice for them. For example: “I'm sorry, Kate, but your cup is empty now because you threw it on the floor. You don't have any more juice.” You might need to explain the consequence more than once, until your toddler makes the connection between throwing the juice and not being able to have it. If they cry out “But I want my juice!” calmly reply that “When you throw your cup and spill your juice, there is no more juice to drink.” Even if they throw a tantrum, hold firm and remain calm. Ignore them (without leaving the room) until they've calmed down, and don't relent and give them more juice. The next time the 2 year old is in a high chair, remind them not to throw their cup, or else there will be no more juice for them. It may take a few tries, but they'll eventually make the connection. For instance, once you hand them the juice cup, say “Now Jordan, remember that if you throw your juice cup, you won't have any more juice to drink.”

Summary:
Permit the behavior that will provide natural consequences. Explain the natural consequence. Reinforce what happened. Offer reminders when they're in the same situation.