I have tried nearly every vocal strengthening product on the market. Many have helped. Buy my all-time favorite product is the Voice Straw H2O 2.0. I love this product and use it daily. I highly recommend it.
I have been struggling to find a suitable plastic bottle for training. I would appreciate it if you could sell the bottle separately, even as an optional accessory.
I was using a just regular stainless steel drinking strap but this is so much better and I got the cup set too which gives you a lot more back pressure which can really help increase your range.
These tools are utterly indispensable and I use them for each and every vocal warm up session.