I've only seen one episode of Shark Tank, and the dopes hosting the show were oohhing and ahhing over some guy's product that allowed a person to place a top on/over a household plate, thus turning it into Tupperware. I had thought up the same invention for canned goods that seemed more realistic. Basically, if I open a canned good and I don't use the entire thing, refrigerator storage can be complicated. Most people take the item out of can and put it in a storage container. I want to leave the product in the can, and just attach a top to it. Since most canned goods are about the same size, it seems a top that fits the standard circular shape of a canned food container would be an easy design..... Unless of course you have a can of anchovies or Spam!
The real problem with my invention is BPA contamination. Remember all those BPA infused Nalgene bottles that trustafarians carried around like Rosary Invocations? A few years back, they were suddenly a health hazard, and everyone had to replace the containers that they used for carrying liquids (anything from baby bottles to hiking canteens). As far as I know, most canned goods use BPA plastic to line the inner portion of the can, so my invention might not be marketable, but for those who don't care, you might be able to make a few sales with it.