It seems obvious - the first thing your customers see when they pull up to your restaurant is the outside appearance. It's important to make a good first impression and create a clean atmosphere to welcome in your guests. Below are a few suggestions on what you can do to keep that "clean curb-appeal".
Garbage/Trash enclosures are often collection areas for litter, windblown debris, and even little critters & pests. Ignoring these can lead to bigger problems as the temperatures peak. First, remove all trash/garbage from the enclosure as well as items that have fallen in behind/beside. If appropriate, use a pressure washer to thoroughly clean the inside of the enclosure including any lining containers. Make sure to use an appropriate sanitizing agent to remove any dirt, debris, rodent droppings, or smell. Double check that the area is clean and secure to prevent uninvited guests (pests) from "setting up shop". Have your pest control specialist examine the area and place preventative measures as appropriate.
Parking Lots and Drive Thrus
Think of your parking lot and your drive thru as the first impression of your restaurant. You know you only get one chance to make that impression. It's important to do frequent walkabouts and report any damage and to get these areas shining. Again, a pressure washer can do great work against stubborn stains. Remove any debris (cigarette butts, gum, *masks*) that has accumulated, report curb chips and potholes that could cause tripping/safety issues, and note any touchup (or more) painting that might be required.
Outdoor Dining Areas/Picnic Tables/Bike Racks
Outdoor dining areas, picnic tables, and bike racks are great ways to add value to your restaurant. Make sure to check for any damage that might require sanding, grinding, or painting. Check on any signage that might be required to make sure it's mounted properly and professionally (nothing looks worse that a loosely laminated sign posted with tape).
Gardens and Flowers
I'm definitely not a green thumb and cannot offer any personal advice on what to plant and where. I do know, however, that a nicely planted garden can make the outside of a restaurant (or any place) feel more inviting and appealing. Perhaps there are members of your team who would love a day out of the drive thru or kitchen to help organize and/or take charge of that area of the business. You might be pleasantly surprised with what they can do.
What your restaurant looks like from the outside is what your customers will perceive on the inside (not so unlike how we judge each other I suppose). Perhaps ask your team if there are volunteers to work an outside shift to do a spring cleanup and help make the restaurant shine. Give them the tools, layout the guidelines and expectations, and let them take pride in getting the restaurant looking as inviting as they are.