Omg, I just found out my fiancee has a secret addiction to flavored water packets (seriously, she has 3 gallon-sized ziplock bags full of them). So I'm going to try mixing some in with small servings of soylent and see which work. I'm hoping they don't taste too chemical with the artificial flavorings.
As for teas/replacing water, I really enjoy using my keurig to add a cup of chai tea latte, cocoa, or caramel cappuccino in place of some of the water occasionally. I don't really brew my own chai tea, but I have used Tazo and Oregon Chai tea latte concentrate as well (you don't need a lot, it's normally diluted with milk when making chai tea lattes).
Edit: Black teas should be steeped in much hotter water (just off boiling) compared to most teas. As for how long, that really depends on you, if steeping in pot 2 tea bags 5 minutes, in cup 1-2 minutes, if you're going for strong tea, steeping for 15 minutes, or until liquid is tepid, should be more than enough.