This is a box...of cake! There is likely a loaf of rectangle cake inside this box, the same shape as the box. It's clearly an early piece, with the "Segasonic" logo, but the only other word is "Castella". What is that? A special type of Portuguese cake that Japan became fond of. Read about Castella. The picture is no help, it shows Sonic being helped by a dolphin, while a sunfish (molamola) watches. The side panel has a little Eggman on it, so it's pretty much completely irrelevent to the cake-ey contents. Do you know where this was sold? Write in for credit!
Were there 2 boxes for 2 different Castella Cakes...or is this just the 'other side' of the box you see above? It has the same format (handle on top, rectangle) and a similar ocean theme. However this one has Sonic & Tails on a tiny island that they barely fit onto, with 1 palm tree. There's a catamaran & (oddly, tropically) the little walrus animal that came out of the robots has a life preserver ring. It is curious to use ocean themes for boxes of cake.