I just feel that punishing kids with things that are hot or spicy or soapy will scare them away from trying new things in the future. I seriously doubt my kid would eat chips and salsa, try Indian or Thai food, or eat half the stuff we like if we punished her with hot sauce. I do agree that taking something away when it is thrown is a better idea, and keeping it is just fine. Even though they may seem defiant and awful, in reality kids just get frustrated because they want to please you and sometimes we don't notice all the things they have done already so they get angry and don't know how to explain themselves. They burst into tears, whine, or freak out in anger. It's very frustrating being smallish and smartish and aching to have a say in something important.
We go to a parenting and family nights run by www.onevillagesacramento.org and often there is a lecture on communicating with your tot. Some of the things they talk about are appropriate reactions to things, and one of the best communication strategies we learned was to get down on one knee and become eye level with our daughter and put our hands on her shoulders and really talk to her when she's upset. Communication is not just about talking and expressing, it's about listening, and sometimes the kid just doesn't listen unless you are the adult down to her level. Ditto for us, sometimes we are too busy to "hear" what she's trying to say and the breakdown in the communication leads to a breakdown in the relationship a little. But it's salvagable. There is a control issue, and she's freaking out because she is realizing how little control she has. Maybe your daughter has transition issues? Some kids really need a countdown. Mine seems to breakdown 5 minutes before we have to leave for daycare, tears, stripping of the clothes to put on a dress, lots of no and go away mommy. And I ignore all the "mean" stuff, tell her I love her, and get her moving. sometimes we are just late. I give her some sugarless gum in the car when she settles down. The faster she settles, the sooner she gets her gum, and the morning is more relaxed all around. When she doesn't settle down, no gum, no reward. Those days are very few and far between. Once settled, we talk about things and she helps plan weekends (her big thing is riding light rail. I dunno what that's all about.)
We also read a book by Joy Berry called A Child's Book About Whining (or something similar) and our kid has been really reacting positively when we remind her she's whining. She might still cry, but she tries to get herself back in control.
We also have only one kid, so I am betting a lot of the frustration you are dealing with is because you've got one very smart/insistent 4 y.o. and a baby who really needs even more attention.
Hope something I've said helps!!!