Hi Geoff
I am a mother of T2 18 year old daughter, and I can tell you that you are not the only one feeling this way. My daughter is on insulin (novorapid x 3 and lantus x1). I try to cook healthy for her at home, but I have been told by people they have seen her drinking milkshakes and eating things she shouln't be outside.
I have now come compromised with her that if she doen't be naughty, and don't have this things that she shouldn't outside, then she can have 2 treats each month, and she can eat what ever she wants.
We have 2 set dates. the 10th and 24th.
I will allow her any one sweet stuff she wants, that can be milk shake, ice cream, cakes whatever.
So far it is working well and she looks forward to these 2 days. I am not sure if I am doing the right thing here, but it has helped with her not eating sweet stuff every day.
Hope this helps.