This (for cold brew, at least).

I’ve been using a muslin/“nut milk” bag for years. I’ll grind a pound of coffee and let it steep for a couple of days in roughly a gallon of water, then pour it into a dispenser that I can leave in the refrigerator.

I’m no coffee snob but to me the flavor keeps extremely well.

The only thing I found is that even the finest mesh bag leaves a considerable amount of grit so I pour that through a paper filter. Hard to beat fantastic coffee at the turn of a spigot.