No jinxing just a Beta doing what Bettas do lol!
Wally World and the big box stores have deals and sales on little 1-2 gal set ups, also there are the deals on C....slist probably $25. total for a little 1-5 gal.
The bowl is better than a cup, and I am sure it is going to be a temporary measure.
I kept some Bettas appx. 10 of them with bog plants in the 1.5 & 2 gal vases and the water quality was always excellent and crystal clear, plus did pwc and fed them, they were in the kitchen and kept warm. They would always come over to see what was going on and lived for 3-5 years. Never had tail rot or bloat or other sicknesses. This was years ago btw.
The Arrowhead (house) plants were awesome for the water and they were huge and beautiful.
So...there are worst things for your Betta than a temporary vase. Like someone who doesn't care! Make sure lots of frequent pwc. Easy on the feeding. If you have some plants in there that would be better too for the fish to relax on and for water quality.