I recently purchased (another) insulated sport bottle. I have many...none of them have really been worth while. Either they are too heavy, too weak, or just do not keep things hot or cold. I enjoy my tea on the trail. Fuel is at a premium, so hot water for tea is a luxury, and sun tea only works to a point.
I found a product from Kikkerland - a stainless steel "sports flask". It is the same style and shape as a Sigg bottle, and overall is quite similar in appearance.
It excells in that it REALLY DOES WORK. Hot tea will sill be HOT in 12 hours. It is good and warm after 24 hours. I have used mine every day for 2 months without failure. It comes in three sizes small medium and large with only a couple of ounces difference between the medium 600ml actual volume and the large - 700ml.
The Medium wt is 8.9 oz; and the Large is 10 oz. empty.
These are a bit hard to find...I got mine in Vermont. They are available online from www.Kikkerland.com. The only other mfg is in Australia and they do not ship outside of Australia.
I hope this might solve some problems.
I use it for tea and for keeping my hot water hot for making supper...it I have left over hot water its still hot for breakfast- saves prep time and fuel in the am.