keep some in a glass or vase in yr kitchen and just keep waterin. chop some up and fry em in neutral oil, provides a crispy topping and leaves you with some very useful oil (for salad dressing, sauces, etc). or just munch on em. or just look at them if you like
I wouldn’t recommend just leaving them in just water long term. I’ll usually just buy a new $1 bag of green onions every 3-4 months to keep the onions tasting as fresh as I’d like. You’d want something to act as nutrients for the water if you were to do only water long term.
Piece of advice though, green onions border on being a weed. Realistically, you should be able to plant your bulbs any time of the year other than winter. They will even spread particularly easily.
thank you!