Arguably, a betta wants to be able to swim somewhere that doesn't lead within three milliseconds back to its own butthole, but it doesn't have that luxury. You can't even put them together, because betta fish are the piscine equivalent of endless rage ninjas and they'll just kill each other all day long. Or that's how pet stores market them. In fact, female bettas are generally fine together, and males can live with other species quite often. They also tend to thrive in at least 10 gallons or more per fish, not a bag full of whatever can be scraped from a sweaty teamster's armpit.
These are actually recycled urine sample containers.
Bettas are shipped much the same way you'd ship a boiled hot dog, if that was something you were inclined to do. The shot glass you see them in at the store is actually a relief compared to how they got shipped from the supplier. As it happens, each fish is packed in about an inch of tranquilizing solution at the bottom of a Ziploc baggie. Then they're all packed up in a big bag together and mailed out -- just dozens of little wet sacks with a little fish in them, probably thinking some deep-ass fish thoughts the whole time.
It's said that bettas are shipped this way to keep them chill and to lower costs. No doubt about that second one; god knows shipping bags of water is probably going to set you back a few bucks. But I feel like you'd probably have to be packed in morphine to make a trip in an almost airless bag across the country anything close to tolerable.