A couple of more things to keep in mind (in addition to Karin’s suggestions) is that some Type 1 diabetics do have an insulin pump which is a big help and convenience to them every day. So they will need to adjust their pump’s settings according to their activity level. I don’t want to go into details here, but they need to know what those new settings are because they can affect their training (among many factors). Having juice is a good idea, but also anything else that has sugar and/or carbs will do the job (Fruit Snacks packages which can be found in many stores are great alternative and easy to carry). Some diabetics are in excellent shape and it’s not unusual for many of them to be able to compete in long distance events, so assessing each person individually is the best approach (not one size fits all approach). I hope this helps.