It would be a good idea to inform the host. I try to comply with dietary requirements up to a certain point. Even without prior notice, it would be easy to find some breakfast items in my place, that agree with your diet, as for most guests. But it would reduce temptation if the host knows to remove all snacks from the guest area beforehand. No standard sweets for you as a curtesy 😉
If you rent a private apartment, that is someone's home, you will always have things there, that you may not like, wish to use or could not eat. On the other side, you will also find things that a hotel does not provide.
I understand that having sugar everywhere, may remind you that you should not eat it. Storing these things out of sight seems a good compromise to me. I was faced once with guests who declared themselves Vegan and proceded to empty a storage cupboard, the fridge and the freezer of nearly everything there was, handing over two bags of food at the door. As I had a train to take, I put the dry food into the garage and donated the frozen food to neighbors. I lost over 50 Euros that way and was quite offended that my home had to be purified of forbidden food before it could be used by my guests.
They were very nice people and did not mean it that way, but it felt that way.
Donating a package of sugar to the guardian lady would not be a problem, but if I had to remove the honey too and maybe all open jam jars, which need to be in the fridge, I would hesitate to accept a short booking.
