ok so, just because you add all the medicines and conditioners in the world to your tank it doesn't mean your fish will be happy nor healthy.
Did you cycle your tank before adding fish to it? did you keep up with water changes? were you giving it a proper diet? did you quarantine your fish? did you set up the tank in the appropriate conditions and parameters for a betta? if you didn't then it shouldn't come as a surprise that it died after so little time, also in my experience, no one with a betta in a 1-gallon bowl had a betta that lived for more than 9 months so yeah, no 3 years 1-gallon betta, (actually when I was a mediocre fish keeper I had 1 blue gourami *my favorite non-betta anabantoids* in a 1-gallon tank and it lived 4 years... of the 15 they can live).
if you want to get rid of your 10-gallons and change it for a 1-gallon and stick a betta in it just because you "can't. seem to get it right in the bigger aquarium" then just don't keep fish NEVER again it is that easy.
If you want to have fish but don't want to do any work or buy any products then just get a robofish. keeping fish is keeping a living breathing organism that depends 100% on you so no, fish keeping is not just about enjoying looking at the pretty fish, is doing all the work and taking the proper care based on the proper research of your fish and just then, after doing your daily work and diligence, you can take time to enjoy your fish. Saying that you want to enjoy your fish without doing or buying anything is the equivalent of if your parents had said "yeah I want this baby because it is so cute and funny but I don't want to change their diapers or feed them or bathe them" it just isn't right because the said organism is your responsibility and completely depends on you, if you didn't want to put the work or the money then you shouldn't have gotten it in the first place.
Look, just don't get rid of the 10-gallons, do propper research, scape the aquarium, condition the water, program your equipment, and plan the food you are gonna offer all based on what a betta needs, let the aquarium cycle for at least 2 weeks, and then add your betta, after that, feed once a day, check your water parameters once a week and do a 25% water change once a week, this should give you a betta that lives for more than a few months