I am sorry to hear of how upset you get when your friends eat sweets in front of you, because I am sure they don't realise how this affects you.
Make sure you have a healthy snack with you when you are with your friends and maybe you won't feel so different to them when they start tucking into sweets.
Many young people don't eat sweets for various reasons and enjoy eating a piece of fruit or a healthier snack instead, so you are not alone. It maybe that you just get sad at times about having diabetes, and when you see your friends eating sweets, it makes you feel like you are missing out.
Perhaps you can talk to your friends about your feelings, and I'm sure they will understand more about how your diabetes affects you, will offer more support to you.
I am linking you to info on healthy snacks which I hope will be of help to you, and please remember you are coping very well and this is just a small part of your life to deal with.