above all +100000000000000000000000000000000
Except, you said putting a Bettain anything is a good upgrade from Petco? I'm sorry, but Petco cups are meanat as temporary homes, and the Bettas are supposed to go to loving homes with a big enough tank for them, because really if you buy a Betta and permanently put him in a half gallon vase when it was possible he could have gotten a 3 gallon home then you're ruining his chances at a happy life.
But, if you do go with the vase idea, make sure it is at least 2 gallons. Some say 1 gallon, but actually it's only supposed to be 1 gallons for breeders and temporary conditions /= Because sure a Betta can survive in a small terrible home, but they can't THRIVE. At least, that used to be the view... Also, don't cover the top with a plant or he'll drown. Bettas are carnivors so don't expect him to eat plant roots. Here's a water changing scedule for a vase:
1 gallon= 100% every other day
2-3 gallons- 100% twice a week
4-5 gallons (not vases unless you find a big one) 50% once a week
6+ gallons- 25% once weekly.
Oh, and also, make sure he has plenty of hiding places so he can feel secure.