My VW Beetle won't start without boosting it.

My 2016 VW Beetle won't start unless I hook up my booster pack. After I boosted it I drove it for 3 hours with no issues. Next morning same thing won't start no interior lights even remote door locks wouldn't open. Is it the battery needing replaced because it won't hold a charge or could it be something else? I'm on a disability pension so money is always tight and I don't want to buy a new battery if it's something else. Any advise would be greatly appreciated