I tried their Purple Sweet Potato Charcoal Infused cheese bun ($6.50 + tax). While I'm not partial to sweet potato flavoured desserts, I still found this very tasty.
It had a good bread to cheese ratio, the bread is light and the cheese filling carried most of the flavour. The purple sweet potato one in particular wasn't overly sweet or overly potato-y, which may disappoint purple sweet potato fans. It also had a black crust (I assume that was the charcoal) which was disappointing because it was dry and didn't add any flavour (like you'd get from the crust of your average pineapple bun for example).
Personally I wouldn't order this particular bun again just because the flavour wasn't my thing and it was on the pricier side of their selection, so I would only recommend if you're into purple sweet potatoes or a sucker for "limited time" offers like I am.
Ordered: Purple Sweet Potato Charcoal Infused bun
Price: $6.50 + tax
Final thought: The price range makes these a bit decadent for what they are but their flavour combinations make them interesting enough to give them a try.