Does matcha tea need to be combined with milk or can I use water?
I want to start drinking tea more instead of coffee, I really like matcha tea but whenever I’ve had it it was with milk, but I want to drink more water and want to know if I can mix water and matcha tea?
Also I have a cold brew coffee maker, could I put the powder in the filter as I submerge it? How long would it last in the fridge (assuming I can)?
Matcha is traditionally made with water. Using milk, like in a matcha latte, is a newer trend. Look up a traditional match recipe using a whisk. Note, I know that most people do this with ceremonial grade matcha, but I'm not sure if people do this with lower grade matcha (for example, the bag you might buy at Costco). It sounds like you are probably not using ceremonial grade, so I can't vouch for how good it will taste. However it's still worth experimenting with.
"Cold brew" matcha doesn't really make sense. The goal of cold brew is to extract flavor from coffee/tea leaves over a long period of time using room temp/cold water. However matcha isn't really meant to be extracted, it's meant to be suspended in a liquid and drunk. If you want a "cold matcha drink" rather than specifically cold brew, I would try just throwing some matcha with some cold water in a mason jar, pop the lid on, and shake it up. Then just drink immediately.
You don't remove the powder, it's like instant coffee you just mix it with liquid until it's totally incorporated and you can drink. You can make it cold or hot, whatever you're feeling.
Oh you can drink the powder? You don’t need to remove it?
Nope. Matcha is meant to be ground fine enough such that it suspends in your liquid and is drinkable without filtering.
Is there a tea like matcha that would be good to cold brew?
Sencha or any other green tea can be cold brewed. I've never done it myself, but pretty sure you just throw tea in some water and let it sit for a while. I've never done it myself, so just look up "cold brew green tea." Granted, this will only be like matcha in flavor and not in mouthfeel. Furthermore, if you plan on adding milk, this is probably not the best route to take since green tea is generally much weaker than matcha, so adding milk eliminates any semblance of flavor from the tea.
It's that simple
Yep
By immediately you don't mean in one go right? Like I can drink it in like 2 hours right?
The matcha will settle out if you let it sit. However, you can just shake it up again and then drink it after letting it sit.
Is there a tea like matcha that would be good to cold brew?
Sencha or any other green tea can be cold brewed.
I'd add to this that if you want cold brew green tea that tastes anything like matcha, stick to Japanese greens. Just general "green tea" is IME usually more Chinese in style and a different (though also delicious) beast altogether. Sencha is the quintessential Japanese green tea and most easily available, and IMHO makes a very nice cold brew in summer.
Actually cold brewing might also be a good experiment for any possibly remaining mid-grade matcha you may have, since the method tends to reduce astringency and bitterness; just use it like a normal tea (larger amount) and don't stir towards the end, let the tea powder "gunk" settle at the bottom. I have not tried this.