Necessity is only half of the equation. Something which meets a need can still be excessive, and may not be bought at the right price or in the right quantity.
Coffee, if not a necessity, is certainly a productivity enhancer worth far more than its cost. A coffee drinker can avoid Starbucks, be it in store or home brewed. As far as the utility of coffee is concerned, generic will do just fine, and habitual coffee drinkers would be well advised to purchase multiple cans in a bulk package at a warehouse club.
The same applies for clothing. Clothing is a necessity, and depending on one's job, a certain style may also be a necessity. If you buy clothing frequently at retail, you are paying too much. Make friends with deep clearances and online sellers, and you will significantly cut your clothing expenses without sacrificing utility. Having a detailed budget will help in regards to something like clothing, where it is easy to spend more than you need. By budgeting beforehand, you can make calculated decisions regarding excellent price opportunities without being induced to buy too much by the discounts. If you can meet your needs with less than what your budget allows, then lower your allocation towards clothing to avoid the temptation of overspending.
Food is another excellent opportunity to save money. Buy generic staple items in bulk from a warehouse club. For other items, carefully monitor sales and online coupon offerings to get the right deal.
Put the cash, checks, and debit cards away. If you aren't earning at least 1% on all purchases, and more on specific purchases, then either (a) get the right card, or (

work on fixing your credit to get the right card. The way you pay can accumulate significant savings over the course of a year. The right combination of cash back rewards cards can easily yield above 2% cash back on an aggregate annual basis.