Nov 1, 2017 - 1:42 PM
Welcome to MySwissAlps Helloxoxo!
Personally I would for sure not rent a car for this. If you have a car at your disposal it is an option, but still you would have to park it in Interlaken (paid), and switch to the trains to reach Jungfraujoch. By car, it might be 10-15 minutes quicker to drive to Interlaken, but only if there are no traffic jams. You'll loose that time again finding a parking spot and switching to the train.
I'd recommend to go by train and travel at least one way via Lucerne and the scenic Golden Pass line, if there's daylight during the trip. This route takes more time, but it will be a long day anyway so you might as well make the most of it ;-) If you have no rail pass, a ticket costs CHF 350.80. Perhaps slightly less via the Golden Pass line.
Another option is a guided trip, partly by coach. This is cheaper but you'll have to settle for the pace of the group. You'll find the options here: www.myswissalps.com/ju ngfraujoch/packages.
Does this help?