Non fire/smoke offering alternatives
As someone who is going back to living on campus soon where we can't burn candles/incense/other flames, here's a (non exhaustive) list of alternatives for your spirits/deities/entities
Always a good basic offering that can be applied to most entities, just make sure it's fresh! Other drinks can include juice, milk (good if your Kemetic), and alcohol if you're able to
Again, something that can be applied to most entities. Especially deities who usually have certain foods historically offered to them
Offer crystals associated with your entities or experiment and see what they vibe with
If you have a green thumb, consider putting a plant or flowers on their altar (or whatever their sacred space may be)
(also if you tend to kill plants, cacti or even moss balls are easy to care for and are pretty hardy)
Draw/paint/sculpt something for them! Even if you're not "good" at art, they'll surely appreciate the effort nonetheless!
Things You've Found in Nature
Go on a walk and find some cool rocks or bones or whatever, anything that speaks to you. Offer it to your entities!
Something we've been meaning to do more often. You can use any herbs in your pantry (and you most likely have a carrier oil in your kitchen already)! Use them to anoint yourself or other offerings
One of the more slept on offerings imo, but just do something for your entities! Even simple things like self care can be a devotional act. A devotional act that my deities love is researching/learning about their myths/culture where they come from