Experiment to you own taste. Tea bags may be period, but don't look good. Tea sets are available that contain a tea tin, grater, and compressed brick of tea. They are inexpensive, and give a better look to the camp. To settle coffee ground or tea leaves, add a table spoon of cold water to the pot.
Coffee is coffee.
Often it was sold or issued green, to be roasted as need. Many coffee specialty stores can order green coffee if you want to carry it that far. Small coffee grinders are common, and one can serve an entire unit. For fizzy drinks that are easy to carry, one uses soda powders. In a blue paper is put thirty grains of bicarbonate of soda.