Our favorite brand over the years has been Kucharik. No matter what your outer layer, you'll saturate your clothes in a few hours. Wear the lightest clothes that will keep you comfortable, with a wicking layer like Capilene or Drilete next to your skin. Overdressing and sweating will leave you just as cold as underdressing and will also waste precious water. Carrying a second base layer will let you change into dry clothes about midway into the ride.
Heat packs are small envelopes filled with powdered iron and oxidizers.
They can warm hands, feet or water bottles for hours. Some people use them as part of their standard winter set-up, others carry them for emergencies. Grabber Mycoal is a widely available brand. Bike Set-up Any mountain bike that's good enough for serious off road riding will work for the Iditasport. The top finishers' bikes over the years have mostly been quite standard, with special rims and carefully chosen tires.