It can't be stressed enough how important providing good meals on a set is. It doesn't matter if it's a multi-million dollar picture or a micro-budget short, feeding the cast and crew a nutritious meal is an investment that pays off even long after the project has wrapped.
When planning out your budget, allow ample funds for craft services and/or catering. You don't need to hire a fancy service to cater. With a little planning ahead and talking to managers, you can get some great discounts from local restaurants while arranging to have a PA pick up a feast to deliver to the set.
Pizza and fast food are common standbys. However, with the wide variety of special diets and allergies that people have the chances are good that you'll have at least one person who can't eat it. Always provide a wide variety of fruits, vegetables, meats, and dairy on the menu so your crew can choose what's right for them.
Finding out about allergies or special dietary needs ahead of time is always a good idea, and it makes the job of planning the menu a lot easier. Add a diet and medical info sheet to your paperwork when signing on cast and crew. That way you'll know exactly what type of diets you'll have to accommodate.
For very low budgets, consider having someone cook meals and deliver them to the set. A few bags of groceries can be a lot cheaper than restaurant catering and there are hundreds of simple dishes that can be prepared quickly and set out as a buffet for meal times.
And don't forget the beverages! Asides from the bottled water, it's always a good idea to provide coffee, iced tea, and maybe even lemonade or a fruit punch. You can get large beverage dispensers pretty cheap at discount stores and keep a cooler full of ice nearby. If you shoot frequently, a commercial chilled drink dispenser might be a worthwhile investment.
Providing good meals does a lot more than just feed people. It boosts morale, makes the crew look forward to working with you, and can even boost up your reputation in the long run. It is not uncommon for Green Room chatter to include discussions about who offers great meals and who just serves cold pizza every day.