Ooh, this really kicked off didn't it..
If I go to stay at someones house, they ask if there's anything I'd need, for example if i go to my friends house, she's vegan and doesn't drink coffee.. so she'd say 'will you want anything i don't have' and i might say 'its ok ill bring some coffee' or she might offer to pinch some off her mum who lives upstairs.
If someones coming to mine and I know ive not much in, I might ask what they'd like, offer to get it or if I can't, ill tell them to bring it with them.
If they are sufficiently well known to you to be eating in your home, I think the ability to have sane and sensible conversations like 'I've no fizzy water, if you want that bring it with you' or 'have you got any mayo cos a dry cheese sandwich makes me boak' then... you have got an issue and need to sort it.
I've lived on pennies and scraping together for meals and I've had no problem at all saying 'theres cheese on toast for lunch but we've run out of ketchup, fetch some or do without' to my friends, because they are my FRIENDS.
I might ask, if someone offers me a drink, if they have any fruit tea... but if they say 'no sorry' then thats fine, ill drink something else.
I wouldn't however, be so rude as to say 'in future dear friend, I take fruit tea, not black tea'... thats really snotty!
There are ways of asking and ways of saying no, I don't see why it has to be such a big deal.
Also, am I the only one who thinks the OP just eats DUST?