I have done a bit of research on deity offerings. I have provided a bit of info below, I hope it helps you decide on an offering.
On a side-note, I would meditate on this matter and see what comes to you. What do you feel would be most suited as an offering to your deity? I work with Bastest, personally, and through mediation and communing with her, I've found that anise, lavender, catnip, and rose are things that she likes. They feel very appropriate as offerings, perhaps I should put it that way.
The following list are general offerings if you don't have a specific deity you worship. These are all associated with the God form and the qualities that he (or they depending on your belief) represents.
Offerings Associated with the God:
All fiery and airy herbs. These include: basil, chrysanthemum, snapdragon, clover, lavender, pine, sunflower, pine cones, seeds, cacti, thistles, orange, cedar, and Juniper. Any flowes or herbs associated with Mars or the Sun can also be used.
Crystals and Gemstones associated with the God:
All orange and red stones; stones associated with the Sun, Mars, fire, and air. These include: carnelian, ruby, garnet, orange calcite, diamond, tiger's eye, topaz, sunstone, bloodstone, and red tourmaline.
The following list are offerings specifically for Ra.
Ra: frankincense, myrrh, and olive
Sources: Wicca: A Guide for the Solitary Practitioner -> by Scott
Cunningham
One traditional offering to any of the Egyptian Gods was cool water. Think of it...in a desert country water is a precious thing as all life depends upon it. You might also use frankincense, myrrh, or kyphi incenses as burnt offerings.
I personally, would assist him. The interesting part of Kemetic practices, is that the religious ones often are to assist our netjeru.
A good way to thank Re is simply by creating a small clay or other image of Apep, spitting, stomping, cutting, and generally destroying Apep as you shout at him to die and not rise again, to be cut and not fight against Re, to be destroyed and to not delay Re in his journey. If you can, throw it into a fire as you chant over it.
You can also make or read aloud hymns to Re as the sun rises, calling him strong and powerful, saying he will defeat his enemy (it benefits not to mention Apep here), and generally flattering him.
You can also build an altar or shrine, place an image of Re on it (it can even be simply a printed piece of paper), a bowl for water, a bowl for food, a place for incense, and a place for candles. If you are old enough, a place for libations of alcohol. If not, juice or tea makes a fair substitute. The reason for both water and a libation is that water was an agent used to cleanse, and not something to drink from. Their beer was actually rather weak, but they used it due to the fermentation process ensuring the beer was safe to drink.
If you want to remain traditional, you will also want to purify yourself before going before him; however not all Kemetic paths are traditionally inclined. If you do, check out my post on natron, and also avoid anything that would alter your ability to communicate with him; such as sex, drugs, and illness. These are things that are considered offensive and counterproductive to your goal traditionally speaking.
You can also do something as simple as sending your energy to him with a thank you note attached, but that is less traditional in scope.
If you are interested in any of the traditional aspects, feel free to hit me up for answers, I love to discuss my path.
