Yup. How big are they? Also, just rinsing them out and scrubbing with clean HOT water should do the trick.....I have some of mine in pickle jars....and that worked for me.
Thats not big enough for any length of time. Even as jarring, they should have at least 32 oz. For permanent housing, a 1 gal jar or tank is about the minimum. Then it requires heavy water changes.
While they can live in smaller jars, the bigger than tank the happier they are. Have a betta in a 5 gallon and my girlfriends betta is a 10 gallon. They actually are able to use all the space.
Give em a bigger tank and they will reward you for it.
Fully grown males with their tail can grow to larger than 3.5", so if he had to live in that jar he would never be able to spread out...defintly cruel to keep a betta in a jar of that size.
Walmart has the 1 gal with light, filter, air pump for 9.99. It takes a whilke to condition, and putting the female in a little jar decreases the water quality. I do sit the female in a beanie outside the tank the male is nesting in. Lets me feed her heavy for a day before turning her loose. I'm liking it more than the chimney.