I used to work as a pot-washer in the kitchen of a restaurant and therefore I was the person who used to go to the petrol station next door to buy things for the other staff (waiters/waitresses, chefs, etc) as they weren't able to get away for enough time.

It wasn't unusual for me (16 y/o at the time) to go in and buy:-

    cans of coke
    multiple packs of cigarettes (all different brands)
    tampons/sanitary pads
    condoms
    2 gallons of milk, and  5 or 6 loaves of bread (when the restuarant ran out)
    confectionary
    toothpaste
    etc

I got some very very odd looks from other customers but the petrol station staff soon got used to my bizarre purchases.

It certainly helped me get over any fear of buying these kinds of items.