A bottle with an agitator that helps you make protein shakes.
Blender Bottle
I'd recommend you wait until the price is below $10 to buy it.
This is an awesome way to blend your protein shakes with milk or almond milk. I used to use a spoon to stir protein powder, but it would never blend it all the way. There was always some extra powder at the bottom.
With this thing, you just put your powder into the bottle, along with the agitator (blender ball). Then you pour the milk or almond milk to about half way. Then you shake it for 15-30 seconds and it should be fully mixed in! You can look at the bottom of the bottle to know if there is any powder to still mix in. If the powder sticks, the agitator will break it up and help get it mixed in with a few hard shakes.
A protein shake is like a reward to me after a hard workout. This thing makes it so easy to make. Cleaning it is easy too! You just fill it halfway with hot water from the faucet. Then shake it a bit. Dump the water out. Fill it with hot water a second time. Then dump the water out. Then take the top off, dry the top with a washcloth. Then take the agitator out by tilting the bottle. Dry that with a washcloth. Then turn the bottle upside down over the sink to let the rest of the water come out. Then dry the bottle with the washcloth. Put it all back together and you're all done! It is wide enough that you can clean it with a sponge if you ever wanted to, but you shouldn't have to do that very often. The hot water trick is quick and easy.
If you are wondering what protein powder to use with it, I use NOW Foods Natural Unflavored Whey Protein Isolate. You can use the link to check it out and get my thoughts on it. However, any protein powder will work with this thing.
My blender bottle was from 2012 and I'm still using it every day! It still looks and works great after 5-6 years :)