What can survive in a betta bowl?

You said it yourself- "There is no way that any fish, betta include, can happily survive in a tank that small. Especially without a filter." Personally, I use bowls for plants. Like venus fly traps or African violets.

Why use it for fish if you can wear it as a hat? :D

I like Vulcans idea: find a species of carnivorous plant that's suitable for a fish bowl and the caresheet and potting insturcions for it. These plants usually come from swamps and need high humidity which the bowl helps to keep.

I would reccomend some multicolor gravel, some pond snails, and a spongebob ornament. Amber, bettas should live atleast 5 - 6 years so keeping on alive for almost 1.5 years isn't impressive.

Rocks... marbles... fancy gravel... etc... etc...

You could do a colony of pond snails, as you suggested. Pond snails are nearly impossible to kill unless you're trying.

I think a couple of snails will be perfect since there easy to care for. But make sure you have some sort of lid

Pop corn,cereal,candy goes well in bowels. No fish please

Well I once had a tank maybe smaller or the same size and I had a plant and a happy betta fish that survived in there for a whole good year and a half with no filtration. So in my experience yes a fish can survive in a betta bowl.