When Brent had caffeine withdrawal when giving up coffee, why didn't he drink Coke or energy drinks? The bet explicitly banned coffee, not caffeine.
Brent was allowed to drink decaf without losing the bet, so it seems like the bet was to give up caffeine entirely. Also, Davis has been known to condescendingly lecture people who drink pop about how unhealthy it is. Perhaps Brent would rather put up with withdrawal than put up with that.
In "Whataphobia," Wanda is asked what she fears, and she can't think of anything. But we already know from "Oh, Baby" that she has a serious fear of dentists. She won't even consider making a dental appointment unless she has an excruciatingly painful toothache, and even then she needs some convincing.
If that dentist appointment went well, she may have gotten over her fear of dentists.