It's hard to beat cold-brewed coffee for quality, cost and waste reduction:
6.5L cold water (I use 10L food-quality buckets from the hardware store and fill them to a marked line)
1lb bag of coarse-ground espresso (this is where you spend the money -- quality dark roast from a single grower. No mould!)
11-14 hours in the 'fridge or a coldish larder
Filter through a fine-mesh steel colander or similar and then through a t-shirt or speaker cloth bag or large-sized (compostable) coffee filter into a second identical bucket.
Below the steel mesh, I nest two large coffee filters in two cheapo spaghetti strainers for an extra-clear result, but you can use whatever. If there's any sediment (from fine-ground coffee, eg), let it settle out and pour off the good stuff.
Keeps in the cooler for weeks, heats in moments or drink cold when you need a quick caffeine hit. No bitterness: just strong, strong coffee. Freezes into ice cubes for months. Makes great iced coffee (or just emergency supply when you forget the weekly coffee brew