If there was one everyday item which I used to waste a lot, it was milk. I know this isn't a problem for most people but in a household of one person who doesn't eat breakfast cereal and drinks her coffee black, it can be difficult.
I buy UHT milk to use for tea/coffee when guests call unexpectedly. If I know guests are coming I buy pasteurised milk. The UHT stuff comes in one litre containers but I can buy just a pint of pasteurised and sometimes even less. I can manage to use up the remains of a pint but a litre is a lot of milk!
So I make cottage cheese. Heat the milk to just below boiling point, add a generous squeeze of lemon juice and stir. The milk will curdle. (IT IS NOT THE SAME AS LEAVING MILK TO GO OFF!) Leave it to cool a little then strain it. I use muslin inside my sieve. Leave it until all the whey (a colourless liquid) has drained off then put the cheese to chill in a dish in the fridge. The whey can be used in baking.
It does not have the same texture as a commercially produced cottage cheese but it has more flavour. You may want to add salt.