Yes I have made tea and put in a Sigg. Stays hot for a few hours, unless you also get a Sigg insulation item.

The bottle can withstand this without any problems. But it has no insulation. I use the tip from caj3883 (bottle with additional insulation cover made of neoprene). This combination is quite good for warm drinks in spring and autumn and also protects it from dents and scratches. In winter, when temperatures are very cold, I recommend a thermos bottle.