It's a tricky one, you can punish Sheiks f-tilt with a quick d-tilt (learn to buffer that out of shield! I still need to practice that myself). Mostly I feel like the match up on Ganons part is all about knowing what you can punish and being careful with your shield since most Sheiks are grap happy, and with good reason (Sheiks grabs are amazing). If Sheik is not careful enough you can bait Ganoncide (FYI I won five tourney games with Ganoncides, no one had Ganon experience! If you know this is the case, Ganoncide is a legit option for at least one game) for a quick win, however this really only works in one game, they'll quickly simply grap center stage once your at the edge and spam needles (that's what most Sheiks did against me), but that allows you to recover safely, so scaring Sheik off-stage which Ganoncides is a good thing.
Right now there are a few things a want to test. Firstly when Sheiks descends on you with f-air and follow up with a grab or a jab, I wanna see if Ganon can time a well placed grab between the f-air and the follow up. This works on Greninjas (Greninjas like to do the same, but with nair) descending nair, but only if it's poorly space, if it's correctly spaced you can't punish, you have to shield or retreat (You can see the nair coming and challenge with uair, but that's a different story). It might be the same case with Sheik.
However, the Sheik matchup is one I still need to practice myself and discover some things that are useful and figure out the neutral game.