If you think vacuum sealers are just for products then think again. You can actually use these machines to make some super succulent watermelon. All you have to do is cut up a piece of watermelon and vacuum seal it like you would anything else. What happens is it causes all the juice in it to be sucked in, which ultimately increases the sweetness and darkens the colour. This same technique can also work well with other fruits like pineapple.